The BBC's Emma Paterson: He is one of several suspects

The man had been taken into custody at a central London police station after being arrested on Thursday night.

Police said he was "not a strong suspect", but it is thought officers could make more arrests soon.

The Brixton bomb exploded in a busy market

The arrest followed a "steady stream" of calls to Scotland Yard since it released CCTV footage on Thursday.

The video film showed a white man wandering around the crowded streets of Brixton up to 90 minutes before the bomb.

At a Scotland Yard briefing on Thursday, Assistant Commissioner David Veness said: "This one individual may be a loner acting for his own perverted reasons.

"On the evidence we have and the images we are sharing with you, it's an individual acting on his own."

The first blast happened nearly two weeks ago at the busy Brixton market in south London, injuring 39 people.

It was followed a week later with a second nail bomb in Brick Lane, east London.