Engineering firm's truck among the vehicles smashed under Florida bridge that collapsed - but they refuse to confirm whether they were performing a 'stress test' at the time of deadly accident

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A van belonging to the engineering firm which may have been conducting a stress test on the 'instant bridge' when it collapsed near Florida International University in Miami on Thursday was crushed in the rubble.

Structural Technologies, a national company which offers engineering services, confirmed that one of its employees was among at least six people killed in the bridge collapse.

Two other workers were injured and are in stable condition, the company told DailyMail.com.

A spokesperson for the firm told DailyMail.com that the company could not comment on specifically what its employees were doing at the bridge when it collapsed due to the pending investigation.

Miami-Dade Fire Rescue Department workers work at the scene of the collapsed bridge. A vehicle which appears to be a white van is seen on the left after it was crushed by the bridge. The van belongs to an engineering firm whose employees were working on the site

The crushed Chevy van seen above belongs to Structural Technologies, a national company that offers engineering services

A spokesperson for Structural Technologies told DailyMail.com that it could not comment on what its employees were doing at the site, though it said one of its workers died and two others were injured

Arescue dog and its handler works at the scene where a pedestrian bridge collapsed to search for survivors. The Structural Technologies van is seen on the left 

The company said it plans to fully cooperate with local and federal authorities investigating the collapse.

According to its web site, Structural Technologies offers 'post-tensioning' services to engineering firms.

Post-tensioning is a method of reinforcing concrete structures.

It is a form of prestressing - which means that the steel cables are stressed (pulled or tensioned) before the concrete has to support the service loads, according to ConcreteNetwork.com. 

Florida International University is facing questions over whether it did its due diligence in selecting the companies to ensure that the bridge was safe.

The Florida Department of Transportation said that it was the school's responsibility to choose firms that were 'pre-qualified', according to CBS Miami. 

The state agency said that the firm chosen by the school did not fit the 'pre-qualified' criteria.

FIU President Mark Rosenberg insists that the school went through the proper procedures in selecting the engineers.

'I’m satisfied that the testing that was occurring was consistent with best practice,' Rosenberg said Thursday. 

Authorities said Friday that the cables suspending a pedestrian bridge were being tightened after a stress test when the 950-ton concrete span collapsed over traffic, killing six people only days after its installation was celebrated as a technological innovation. 

As state and federal investigators worked to determine how and why the five-day-old span failed, Florida politicians pointed to the stress test and loosened cables as possible factors, and a police chief asked everyone not to jump to conclusions.

'This is a tragedy that we don't want to re-occur anywhere in the United States,' said Juan Perez, director of the Miami-Dade police. 

Seconds later, the bridge collapsed on the traffic below, leaving dust in its wake 

This is the moment the 950-ton bridge, installed in just six hours on Saturday, collapsed on cars waiting for the lights to change

Experts say that tightening steel cables on this kind of bridge has caused at least one collapse in the past, pointing to an example from Australia in the 1970s

'We just want to find out what caused this collapse to occur and people to die.'

US Senator Marco Rubio tweeted late Thursday that cables suspending the span had loosened, and the engineering firm ordered that they be tightened. 

'They were being tightened when it collapsed,' he said on Twitter.

Experts from the National Transportation Safety Board and the Occupational Safety and Health Administration joined police in taking over command of the scene Friday from first responders, who had spent hours racing to find survivors in the rubble of the 175-foot span using high-tech listening devices, trained sniffing dogs and search cameras.

The $14.2million pedestrian bridge was supposed to open in 2019 as a safe way to cross six lanes of traffic between the FIU campus and the community of Sweetwater, where many students live.

Florida Governor Rick Scott said Thursday that investigators will get to the bottom of 'why this happened and what happened,' and if anyone did anything wrong, 'we will hold them accountable.'

Rubio, who is an adjunct professor at the school, noted the pedestrian bridge was intended to be an innovative and 'one-of-a-kind engineering design.'

When finished, the bridge would have been supported from above, with a tall, off-center tower and cables attached to the walkway. 

That tower had not yet been installed, and it was unclear what builders were using as temporary supports.

An accelerated construction method was supposed to reduce risks to workers and pedestrians and minimize traffic disruption, the university said. 

The school has long been interested in this kind of bridge design; in 2010, it opened an Accelerated Bridge Construction Center to 'provide the transportation industry with the tools needed to effectively and economically utilize the principles of ABC to enhance mobility and safety, and produce safe, environmentally friendly, long-lasting bridges.'

The rescue efforts continued through the night on Thursday as teams continued to search for survivors 

Robert Bea, a professor of engineering and construction management at the University of California, Berkeley, said it was too early to know exactly what happened, but he called it a risky move to use what the bridge builders called an 'innovative installation' over a heavily traveled thoroughfare.

'Innovations take a design firm into an area where they don't have applicable experience, and then we have another unexpected failure on our hands,' Bea said after reviewing the bridge's design and photos of the collapse.

The project was a collaboration between MCM Construction, a Miami-based contractor, and Figg Bridge Design, based in Tallahassee. Figg is responsible for the iconic Sunshine Skyway Bridge across Tampa Bay.

Both companies have been involved in bridge collapses before.

FIGG was fined in 2012 after a section of a bridge it was building in Virginia crashed onto railroad tracks and injured several workers, according to a story in The Virginian-Pilot.

The brand new pedestrian bridge collapsed without warning on Thursday afternoon, crushing the cars below it

Aerial photos show the devastation caused when the structure collapsed, as multiple emergency vehicles rushed to the scene

The bridge was built in order to link up Florida International University's campus with a neighborhood that houses students

MCM, meanwhile, was accused of substandard work in a lawsuit filed this month by a worker injured when a makeshift bridge MCM built at Fort Lauderdale International Airport collapsed under his weight. 

Another dispute resulted in a $143,000 judgment against MCM over an 'arguable collapse' at a Miami-Dade bridge project.

A review of OSHA records, meanwhile, shows MCM has been fined for 11 safety violations in the past five years totaling more than $50,000 after complaints involving its Florida work sites.

Both companies expressed condolences for the victims and promised cooperation with investigators.

Local The FIU community, along with Sweetwater and county officials, held a 'bridge watch party' on March 10 when the span was lifted from its temporary supports, rotated 90 degrees and lowered into what was supposed to be its permanent position.

Rosenberg in a video shared on Twitter Friday that the 'tragic accident of the bridge collapse stuns us, saddens us.'

'The bridge was about collaboration, about neighborliness, about doing the right thing,' he said. 

'But today we are sad and all we can do is promise a very thorough investigation in getting to the bottom of this and mourn those who we have lost.'

Engineering experts say investigators looking into the collapsed bridge will want to know why a central tower which is usually built to support a suspension bridge was not in place when it collapsed onto Tamiami Trail.

Last week, Florida International University’s official Twitter account posted a rendering of the bridge in its completed form as envisioned by the planners.

The rendering shows a tall central column with cables connecting it to the main span.

Engineers say the design is known as a ‘cable-stayed bridge,’ which is a kind of suspension bridge, according to USA Today. 

The bridge did not have the central tower in place, even though experts say it is usually placed at the early stages of construction.

In the absence of a tower, there is usually a temporary support, though in this case it is unclear what the builders were using in the absence of a central structure.

‘Whoever is going to investigate, they will ask the fundamental question: shouldn’t the tower be there, and the cables ready to connect to the structure, when you lift it?’ said Amjad Aref, a professor at University at Buffalo’s Department of Civil, Structural and Environmental Engineering.  

Engineering experts say investigators looking into the collapsed ‘instant’ bridge at Florida International University will want to know why a central tower which is usually built to support a suspension bridge was not in place when it collapsed onto Tamiami Trail on Thursday afternoon

Last week, FIU’s official Twitter account posted a rendering of the bridge in its completed form as envisioned by the planners. The rendering shows a tall central column with cables connecting it to the main span. The city of Sweetwater also released a rendering above

The FIU bridge was not yet open to the public when it collapsed onto the eight-lane highway below, killing at least six people and injuring at least 10. It is seen above after it was installed last Saturday and before its collapse on Thursday

‘That’s a question for them to answer.’

Cable-stayed bridges are built in stages. First, planners will locate a clear piece of land with stable ground and a good location.

They will then conduct a subsurface investigation which involves lab testing on the soil to make sure that any proposed structure would be supported by the geological conditions at the site.

If those tests permit, engineers would then erect piers – the upright supports for a structure like a bridge or an arch - and the support span.

After building the main piers, engineers usually begin construction of the central tower.

After the tower is built and the stay cables are installed, engineers then begin work on extending the central span. 

When asked about why there was no central column built before the span, the head of the National Transportation Safety Board, Robert Sumwalt, said: ‘That’s part of our investigation.’

The NTSB is an independent federal agency that probes transportation-related accidents.