Two women killed when a giant, inflatable sculpture blew into the air fell to their deaths from a great height, according to ambulance staff.
Both victims had been on the structure with young relatives
Another 13 people were hurt when the Dreamspace artwork was lifted into the air at Riverside Park, Chester-le-Street, Co Durham on Sunday.
Forensic teams examining the artwork's moorings have not ruled out foul play.
Claire Furmedge, 38, from Chester-le-Street, and 68-year-old Elizabeth Collings from Seaham, died.
Ms Furmedge was a mother-of-two and Ms Collings was a grandmother. Both were on the artwork with young relatives, none of whom were seriously hurt.
A three-year-old girl - Rosie Wright from Langley Park near Durham - was badly injured after being crushed when the sculpture landed on her, according to ambulance staff.
She was apparently spotted in the collapsed structure by a passing anaesthetist, who accompanied her in an air ambulance to Newcastle General Hospital, where she is in a stable condition.
Eight people were taken to the University Hospital in Durham, and others to hospitals across the region.
Beryl Davison, who works for the North East Ambulance Service, was one of the first emergency personnel on the scene.
She said: "There were two fatalities that had fallen from a great height from being thrown out of the inflatable.
"The other major casualty was the young girl who I believe had been crushed when it had landed.
"Where the inflatable had landed there were people underneath so they had been crushed, and there were other, quite traumatic injuries where people had been thrown out and fallen quite a long distance."
Sunday's incident is being investigated by the Health and Safety Executive and Durham police.
A specialist engineer has been drafted in to examine the structure's design, accident investigators said.
A spokesperson for the Health and Safety Executive said: "The deflated structure, ropes and anchor pins have been taken into possession by the police."
Chief Superintendent Trevor Watson, of Durham Police, said officers were pursuing all lines of inquiry following the deaths on Sunday.
He said: "We haven't received reports that is was particularly windy at the time of the incident.
"It is too early to speculate on the cause and we are keeping a very open mind."
Tony Galloway, director of development services at Chester-le-Street District Council, said a trauma helpline had been set up.
"We recognise there will be lots of people who witnessed what happened and may need professional care and counselling," he said.
The Dreamspace sculpture, created by artist Maurice Agis, comprises several rooms, made of translucent PVC sheets, which are interconnected and inflated to allow visitors to walk about inside.
Dragged into air
The artwork has appeared at venues around the world.
Mr Agis' girlfriend, Paloma Brotons, told London's Evening Standard newspaper that the 74-year-old was himself dragged into the air while using extra ropes to tie down the inflatable because of the heat.
She said: "I saw him flying with it and I thought he was going to be killed. There was a team of us that helped to tie the structure to the ground. We even used more ropes because it was hot."
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