Police on Sunday arrested a third man in the same south London (search) area where two men previously were detained and in the same neighborhood where the man killed by police had lived.

The man was arrested late Saturday "on suspicion of the commission, investigation or preparation of acts of terrorism," a police spokeswoman said on customary condition of anonymity. The man was taken to a central London police station for further questioning, the spokeswoman said.

Metropolitan Police Commissioner Sir Ian Blair (search) said earlier there were similarities between the explosives used in Thursday's failed bomb attacks and those detonated July 7. But he said investigators still had no proof the two strikes were linked.

"The equipment in the bombs had all the elements that it should have but it didn't work," Blair told Sky News TV, referring to the explosives that failed to detonate properly Thursday on three subway cars and a double-decker bus.

"It had some similarities" to the devices used in the July 7 bombings on three subway trains and a double-decker bus, killing 56 people, including the four attackers.

When asked if Thursday's attacks were connected to those of July 7, Blair replied, "We have no proof that they are linked but clearly there is a pattern here."

Two of the suspected July 7 bombers, Mohammad Sidique Khan (search), and Shahzad Tanweer (search), went whitewater rafting in Wales three days before the attacks, according to the National Whitewater Centre.

Police refused to comment on a British Broadcasting Corp. report, attributed to unidentified officials, that said authorities were examining whether those involved in Thursday's attacks were on the same trip.

Police have made two arrests after Thursday's botched attacks. Officers have not released the identities of those detained.

But Blair added that officers were "still anxious for any sighting of the four individuals" who carried out Thursday's strikes. Closed-circuit TV stills of the suspects were made public last week.

Police carried out several controlled explosions to dispose of a suspect package found in northwest London, which they said may have been linked to devices used in the botched July 21 attacks.

They refused to elaborate.