An area of Plymouth City centre was evacuated by armed police
Armed police have detained two men in an operation linked to an explosion in a restaurant in Exeter.
Officers targeted the men at a cafe in the Old Town Street area of Plymouth. One man was arrested and the other is described as "helping police".
The operation is linked to Thursday's explosion in Exeter, for which Nicky Reilly, 22, has been arrested.
Meanwhile, sources close to the investigation revealed police were aware of Mr Reilly prior to his arrest.
In Friday's operation, armed police targeted two men who were drinking at the Bagatelle cafe in Plymouth.
Footage of Plymouth police swoop
Tony Merrick, who works nearby, told BBC News: "There were about 25-30 officers in 10 vehicles.
"They sealed off the area and two men in the cafe were surrounded."
Rebecca Pope, 25, who was looking out of a window above the cafe, said the two men were put in paper suits before being taken away in unmarked cars.
BBC Home Affairs correspondent Daniel Sandford says Mr Reilly became known to officers because he was close to a group which police had been gathering information on.
It is also understood Mr Reilly received a text message before he travelled to Exeter, which could be significant to the investigation.
Police arrested Mr Reilly, from Plymouth, on Thursday after an explosive device detonated inside the Giraffe restaurant in Exeter.
It is thought there were two further devices which were recovered from the scene and made safe.
Our correspondent said the devices contained nails, drain cleaner, kerosene, an organic oil and aluminium foil.
He added that it is not yet known if the explosion was caused by a deliberate or accidental detonation.
Officers later revealed Mr Reilly, who was injured in the blast, had a history of mental illness.
Deputy Chief Constable Tony Melville said on Thursday evening police believed Mr Reilly had adopted the Islamic faith and had been "preyed upon" and "radicalised".
However, Devon and Cornwall Police have not since elaborated on these claims.
Nicky Reilly suffered facial injuries in Thursday's blast
Neighbours of Mr Reilly have told BBC News he converted to Islam and changed his name to Mohammed Rasheed.
Police said Mr Reilly boarded a number X38 double-decker Stagecoach bus in Bretonside bus station, Plymouth, on Thursday morning and have appealed to passengers on the service to contact them.
"We know that between 1026 and 1040 yesterday morning 54 other passengers boarded the same bus and travelled to the main bus station in Paris Street, Exeter, arriving just after midday," a spokesman said.
The explosion took place at about 1250 BST.
He was taken to hospital following the explosion where he remains under police guard.
A bomb disposal team arrived at Mr Reilly's home in the Stonehouse area of Plymouth at lunchtime on Friday.
Police investigations are continuing at the flat, while the cordon at Old Town Street has been lifted.
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