LONDON – Police raised the death toll today to at least 49 from London's terrorist bombings but said more bodies were trapped in a subway car deep underground. About 100 wounded were hospitalized overnight.

Commuters reluctantly returned to the Underground, but buses and subways carried fewer riders than normal.

Sir Ian Blair, commissioner of the Metropolitan Police, said the bodies of 13 people killed on the double-decker bus that was hit Thursday had been recovered, giving the first official tally from the bus blast.

The police press office said the overall death toll from the four attacks was 49 but they expected it to go higher because they have not accounted for all the dead on one subway train.

"The tube train at Russell Square still contains a number of bodies which have not yet been retrieved, we do not know how many there are there," Blair said.

Police said investigation and recovery were hampered at a bomb site because of fears the subway tunnel was unsafe. Engineers were examining structural damage. More than 700 were injured in Thursday's attacks on London — the worst attack in the city since World War II.

London calling

For information about American citizens who may have been affected by Thursday's bombings in London, call 888-407-4747 (toll-free in the U.S.) or 202-501-4444 (regular toll line from outside the U.S. and Canada).

Blair said that 22 were in serious or critical condition. The injured included citizens of at least five countries in addition to Britain — Sierra Leone, Australia, Portugal, Poland and China. One person died in the hospital, where 100 victims spent the night, Blair said.

Earlier he said the death toll would be "50-plus" because police have yet to account for all the dead on one subway train. French Interior Minister Nicolas Sarkozy also said Thursday that the death toll was 50, citing a conversation with his British counterpart.

The driver of the No. 30 bus that was hit said the double-decker had been diverted from its normal route because of the earlier disruptions on the subway.

"My bus had been diverted because there were thousands of people coming out of the Tube. There were many people who were trying to get on the bus at once," said 49-year-old George Psaradakis, who suffered minor cuts and bruises. "Suddenly there was a bang, then carnage. Everything seemed to happen behind me."

Authorities have said the attacks had the signatures of the al-Qaida terror network and current and former American counterterrorism officials said they were taking seriously an Internet claim of responsibility by a group calling itself The Secret Organization of al-Qaida in Europe.

Little was known about the group, but a Web statement in the same name claimed responsibility for the last major terror attack in Europe: a string of bombs that hit commuter trains in Madrid, Spain in March 2004, killing 191 people.

Blair said there was no evidence proving that the attacks involved suicide bombers but that officials hadn't ruled out the possibility.

The blasts paralyzed the city's public transportation system, halting subway service, delaying buses and stranding thousands of residents and tourists.

Shows across London's West End theater district were canceled Thursday but performances were resuming Friday. Weekend concerts by Queen and REM in Hyde Park also were postponed by a week because of safety concerns.

London's mass transit system reopened Friday, though some commuters, admitting they were afraid, opted for a taxi. Normally packed double-decker buses carried just a handful of passengers, and many Underground stations were less congested than normal. But others said they had little choice but to board the subway.

"I was scared, but what can you do?" said Raj Varatharaj, 32, emerging from an Underground station. "This is the fastest way for me to get to work. You just have to carry on."

Assistant Police Commissioner Andy Hayman said officials believe the bombs were placed on the floors of the three subway cars that were hit. He said the initial investigation suggests that each bomb had less than 10 pounds of explosives. The weight of explosives was smaller than recent bombs detonated in the Middle East.

Based on evidence recovered from the rubble, investigators believe some of the bombs were on timers, a U.S. law enforcement official said. The official would not further describe the evidence.

Investigators doubt that cell phones — used in the Madrid train attacks a year ago — were used to detonate the bombs in the Underground because the phones often don't work in the system's tunnels, the official said.

Police denied that they had found any unexploded devices. Two suspicious packages in other areas were destroyed in controlled explosions, but Blair said they turned out to be harmless.

Security officials locked patrons inside the British Museum briefly Friday after guards spotted two suitcases found chained together inside the museum. Doors were unlocked after they located the bag's owners, two tourists.

Thursday's subway blasts went off within 26 minutes, starting at 8:51 a.m. An explosion ripped the roof off a double-decker bus less than an hour after the first bombing, attacks that came as world leaders were opening the G-8 summit in Scotland.

Prime Minister Tony Blair, who just the day before had been basking in the glory of Britain's successful Olympics bid, condemned the attacks and blamed Islamic extremists. Foreign Minister Jack Straw said the attacks bore the hallmark of al-Qaida, the group responsible for Sept. 11.

Ten of London's 12 subway lines reopened Friday, though service on three was restricted. Bus service was running through central London, except for diversions around blast sites.

Aldona Mosjko, a 21-year-old bagel shop manager from Poland, was among those too frightened to take public transportation Friday. "Normally, I take the bus, but today, I took a taxi. I was a bit afraid," she said.

Stocks were higher in Europe on Friday, with insurance and travel-related stocks regaining some of the ground they lost on Thursday.

Queen Elizabeth II, her son Prince Charles and his wife, Camilla, Duchess of Cornwall, meanwhile, made separate visits to bombing victims at hospitals in the capital.

The queen expressed her admiration for all the Londoners who "are calmly determined to resume their normal lives."

"Sadly we in Britain have been all too familiar with acts of terror and members of my generation, especially at this end of London, know that we have been here before," she said during a visit to the Royal London Hospital, referring to the Nazi air blitz of World War II.

"But those who perpetrate these brutal acts against innocent people should know that they will not change our way of life," she stressed.

Some commuters commented on what appeared to be a light police presence at some Underground stations.

"Everyone is very quiet, everybody is a bit anxious," said Anil Patel, 40, a banker. "An obvious (police) presence would have settled your nerves."

The Secret Group of al-Qaida's Jihad in Europe claimed it was behind the attacks in a posting on a Web site, saying the bombings were punishment for Britain's involvement in the war in Iraq and invasion of Afghanistan.

It threatened to attack Italy and Denmark for their support of the U.S.-led coalitions in both countries, too.

A senior U.S. counterterrorism official said Thursday that the Internet posting was considered a "potentially very credible" claim, in part because the message appeared soon after the attacks and didn't appeared rushed. The officials spoke on condition of anonymity because investigations were ongoing.

Investigators said they would look for evidence in the debris from Thursday's attacks and in the video footage from some 1,800 cameras in London's train stations.

Charles Shoebridge, a security analyst and former counterterrorism intelligence officer, said detectives will have to watch thousands of hours of video — slowly and carefully. Investigators will try to find on tape the point at which bombs were placed, then trace back the movements of the bomber, a task he said could involve hundreds of cameras.

Much of Europe also went on alert, and Italy's airports raised alert levels to a maximum.

Associated Press writer Katherine Shrader in Washington contributed to this report.