A man arrested after an explosion at an Exeter restaurant has "a history of mental illness" and was a recent convert to Islam, police have said.
Nicky Reilly, 22, from Plymouth, suffered serious facial injuries when a device detonated at the Princesshay shopping centre in the city.
He is now in police custody in hospital and officers have also searched an address linked to him in Plymouth.
A senior police officer said Mr Reilly had been "preyed on and radicalised".
Anti-terror police and security services are assisting the inquiry.
Mr Reilly was arrested after the explosion at 1250 BST on Thursday in the Giraffe restaurant in the £230m shopping development, which is one of Exeter's main attractions.
CCTV footage taken from a nearby camera appears to show him emerging from the cafe with blood pouring down his face before his arrest. No-one else was hurt in the explosion at the restaurant, which was busy at the time and is popular with families.
Amateur footage of the aftermath
Another device, which did not go off, was found outside the premises.
After the incident, officers evacuated the city's bus station - which is about half a mile away - and extended an exclusion cordon 100 metres around the scene. However, police have now re-opened the city centre though the restaurant remains closed.
Devon and Cornwall Police Deputy Chief Constable Tony Melville said: "Our investigation so far indicates Reilly, who had a history of mental illness, had adopted the Islamic faith.
"We believe, despite his weak and vulnerable illness, he was preyed upon, radicalised and taken advantage of."
After the arrest, police evacuated some properties 40 miles away in the Stonehouse area of Plymouth before officers from the Tactical Aid Group searched a flat in King Street, Plymouth, which was linked to Reilly.
They confirmed he travelled from Plymouth to Exeter by bus and are appealing for anyone who may have seen him over recent weeks to contact them.
Officers would like to know more about Mr Reilly and trace his recent movements.
Police have been searching a flat in Plymouth
Neighbours have described Mr Reilly as a "big friendly giant" and told BBC News they were shocked at what had happened.
Businesses in the vicinity have been asked to retain any CCTV footage which could assist police.
Eyewitness Peter Lacey, who was in the restaurant with his wife, told BBC News: "There were three explosions. It is my impression they sounded more like gunshots than a bomb, like a lightbulb exploding.
"They came from a locked toilet."
The £230m Princesshay development officially opened last September. The scheme has been heralded as the biggest single investment in regeneration in the city's history.
It contains a mix of shops, restaurants and apartments.
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