Nobody has been arrested so far over the deadly London bomb attacks, in which at least 50 people were killed and over 700 injured, Commander Brian Paddick of the London Metropolitan Police told a news briefing Saturday.

The criminals are still "at large", while massive search for the attackers are underway in London and throughout the world, he said.

However, the Sky TV reported that an internet statement said Saturday al-Qaeda was responsible for the deadly bomb attacks in London.

"A group of mujahedeen from a division of the Abu Hafs al-Masri Brigades piled blow after blow on the infidel capital, the Britishcapital, leaving dead and injured," said the Internet statement.

Paddick told the news briefing that three explosions went off within seconds or almost simultaneously in London Thursday,

Paddick said that new finding tells that the explosions were "almost simultanuous" not as what believed to be within minutes or even longer.

Timing devices were likely used to set off the three bombs that caused carnage in the London Underground system, he said.

The roof of the double-decker bus where at least 13 people were killed, will be taken away for examination, he added.

Russel Square, a tube station in central London will remain closed as condition there were "extremely difficult" Paddick said.

Source: Xinhua