British police investigating last Thursday's bomb attacks on three London underground (subway) trains and a city bus say they have evidence that at least one bomber died in the attacks, and they are trying to determine whether all of them died. Police also announced their first arrest in the case. 

Deputy Assistant Commissioner Peter Clarke, who heads Scotland Yard's anti-terrorism branch, says the investigation quickly led police to suspect four men.

"We are trying to establish their movements to the run-up to last week's attacks and specifically to establish if they all died in the explosions.  We now know all four of these men arrived in London by train on the morning of Thursday, July the 7th. We have identified CCTV [closed circuit television] footage showing the four men at the King's Cross station shortly before 8:30am on that morning, July 7th."

Mr. Clarke said investigators have found personal documents belonging to three of the four men near to three of the blast sites.  He said they also have strong forensic evidence indicating one of the bombers died in the explosion at the Aldgate underground station.

Mr. Clarke said three of the suspected bombers are from the northern county of West Yorkshire, where early morning police raids in the city of Leeds led to the arrest of one individual, who was taken to London for questioning.

Police stand guard on Hyde Park road in Burley district of Leeds, England
More than 500 people were evacuated from the area and streets were cordoned off as part of the operation, which involved military experts blasting their way into one of the homes.

In another development, police used controlled explosions to deal with a car in Luton, 50 kilometers north of London.

Mr. Clarke explained. "At Luton, a vehicle has been found in the station car park, which we suspect is connected to this investigation. Again, steps are being taken to ensure there will be no risk to the public."

Officials say they have taken several hundred witness statements and have received more than 2,000 helpful telephone calls from the public.  Police are also examining tapes from more than 2,500 closed circuit television and security cameras around London, and have urged witnesses to e-mail them photos or video taken from their cellular telephones.

Fifty two people have been confirmed killed in last Thursday's attacks, and some 700 others were injured. Officials say the death toll could still rise.