LONDON -- Police are raising the official death count in last week's London bombings to 54, and London's police chief says detectives believe all four blasts last week were suicide bombings.

A police statement says one of those injured in the blast on a double-decker bus has died of his wounds.

Ian Blair also told reporters Thursday that police have identified the four people carrying the bombs. It's the first time that police have said publicly that the attackers were suicide bombers.

Ian Blair would not comment on reports that three of the four bombers were Britons of Pakistani descent. The BBC and Sky News also report that police believe the fourth bomber was a British resident who was born in Jamaica.

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Authorities suspect the four attackers didn't work alone and that their co-conspirators or leader are likely still at large. Blair wouldn't say how many suspects might still be on the loose, but he did say investigators are trying to determine who planned the attacks. He also noted the attacks have all the hallmarks of al-Qaida in the way they were carried out.

Meanwhile, people across Europe paused for two minutes of silence Thursday to honor the victims of last week's bombings.

Much of London came to a halt as Big Ben chimed at noon. Tourists and Londoners alike stopped on sidewalks outside Parliament and bowed their heads.

At Buckingham Palace, Queen Elizabeth stood silently in the main gateway to the palace. Buses and taxis came to a halt. Landings and takeoffs from Heathrow Airport were suspended so planes wouldn't disturb the silence.

Elsewhere, sirens wailed across Paris. In Berlin, subway trains, trams and buses stopped for two minutes. In Turkey, a predominantly Muslim country hoping to start EU membership talks this fall, leaders interrupted a meeting in Ankara to stand in silence.

British police are pursuing a fifth bombing suspect who may have masterminded the London attacks. According to an unidentified source quoted in The Times of London, detectives are looking for Magdy el-Nashar, 33, an Egyptian-born academic who recently taught chemistry at Leeds University. The newspaper said he was believed to have rented one of the homes being searched in Leeds.

Meanwhile, residents in the section of of Leeds cordoned off by police are being allowed back into their homes. Police said they found no hazardous material in a home they'd searched.

The home in the city's Hyde Park neighborhood was identified in some media reports as a suspected terrorist bomb factory, but police and army explosives experts had spent two days searching the home with no luck. It was one of a-half dozen residences raided Tuesday after police determined that three suspects in last week's London bombings came from the Leeds area.

Police also continue to hold a 29-year-old man who was arrested during the Leeds raids. And investigators in London continue searching through evidence from the explosion scenes and from closed-circuit TV footage from city surveillance systems.

Details Emerge On Suspects

Details emerged Wednesday about the lives of four suspected bombers, one of whom was only 19 years old. Three of them were believed to have been killed in the bus and subway explosions.

One was a cricket player. The 19-year-old was described as a flirt, who wore lenses to color his eyes blue. And a third man who's being mentioned as a possible suspect in London's suicide bombings was a counselor at a youth center.

Police haven't named the men they think orchestrated the London bombings, but families and neighbors have. And the people of Leeds, a working-class community, are asking what might have driven these British citizens of Pakistani descent toward such violence.

Friends of Hasib Hussain, the 19-year-old who is suspected of bombing the double-decker bus, said he was known for his sense of humor and his style.

And 30-year-old Mohammed Sidique Khan worked with disabled children, and leaves behind a wife and infant daughter.

Relatives of Shahzad Tanweer, the athlete, said he was devout, and they're shocked he's being linked to such violence.

Bashir Ahmed, Tanweer's uncle, said his family first thought the 22-year-old had gone to a religious gathering. Three days later they realized he was gone, later to be named by news reports as one of the London bombers.

His nephew was very religious, often went on trips like that, and rarely talked about politics or read a newspaper, his uncle said. Tanweer would sit around all night to watch cricket, his favorite sport, but never sat five minutes to watch the news, his uncle said.

Ahmed calls his nephew "the kindest, loving, caring person" and says he can't understand how he could have been involved in the attacks.

A fourth potential suspect spotted with the others has yet to be publicly identified.