Nicky Reilly was injured in the explosion
Police investigating an explosion at a restaurant in Exeter are questioning a third man.
Two men are already in custody after an explosive device was detonated at the Giraffe restaurant last Thursday.
Nicky Reilly, 22, from Plymouth, was arrested after he suffered facial injuries in the blast.
Another man who was arrested by police in Plymouth on Friday is still being questioned. Police have not named him or the latest arrested man.
Devon and Cornwall Police Assistant Chief Constable Bob Spencer said officers made the third arrest at 1730 BST.
A fourth man detained in Plymouth on Friday is "continuing to assist police with their enquiries" but is no longer being held in custody.
On Thursday morning police were granted a seven-day extension to question two of the suspects.
Meanwhile searches continue at a number of premises in Plymouth, including the Muslim Community Centre in St Jude's, as part of the investigation.
ACC Spencer said: "The force has begun a search at the Muslim Community Centre.
"This search, as well as another being carried out at a residential address in Plymouth today, are both linked to the arrest of the man made earlier in the day.
"No arrests were planned or made at the community centre.
"As our investigation is ongoing we would reiterate our plea to the public not to make assumptions about people's involvement in this case based on their appearance, ethnic origin or faith."
A spokesman from the centre said: "The trustees of the Muslim Community Centre at St Jude's are as shocked as everyone by the recent events that have unfolded at Exeter and Plymouth.
"We have been working in partnership with the police and community to build the centre and we are now committed to assisting the police with their enquiries."
Under anti-terrorism legislation, suspects can be held for 28 days.