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Hasib Hussain is pictured carrying a rucksack at Luton station as he made his way to London.

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LONDON, England (CNN) -- Police appealed for information Thursday on the movements of the man they believe blew up a double-decker bus in London a week ago, one of four bombings that also included three subway trains.

Meanwhile, officials with knowledge of the investigation confirmed to CNN the name of Germain Morris Lindsay as the fourth man suspected in the bombings. No other information was available.

A Scotland Yard spokesman said the death toll in the bombings had risen to 54 after a man wounded in the bus blast died in a hospital; 13 others on the bus also died.

Some 700 people were wounded in the four bombings. Forensics experts have said it could take weeks to identify all the bodies recovered, many of which were mangled. Ten have been officially identified so far.

In their appeal to the public, British police released a CCTV image of Hasib Hussain with a rucksack on his back as he made his way through Luton railway station at 7:20 a.m. en route to London the morning of the attack.

"We know he traveled from West Yorkshire and arrived in London with three other men," said Deputy Assistant Commissioner Peter Clarke, head of Scotland Yard's antiterror branch. "We need to know his movements until 9:47 a.m."

Once in London, he boarded the No. 30 bus. The bomb went off after the bus stopped in Tavistock Square, nearly an hour after the first three explosions on the Underground trains.

Clarke said the 18-year-old Hussain died in the blast. "We now believe he was responsible for this attack," he told a news conference. Police sources said documents belonging to Hussain were found amid the bus wreckage.

Clarke said police wanted to know what Hussain was doing in the hour after three suspected fellow bombers simultaneously blew themselves up on trains. They detonated their devices at 8:50 a.m.; the bus bomb went off at 9:47 a.m., Clarke said.

Clarke said he could confirm that Shahzad Tanweer, 22, was believed responsible for attacking the subway train between Liverpool Street and Aldgate Stations. Police sources said documents belonging to Tanweer were found at the blast site. (Family shattered)

Tanweer and Hussain were from Leeds, West Yorkshire, 200 miles north of London. Both their names were previously confirmed to CNN by officials familiar with the investigation.

On Wednesday, officials familiar with investigation also identified Mohammed Sadique Khan, 30, of Dewsbury, West Yorkshire, as another of the suspected bombers.

Documents belonging to Khan were found in the debris of the Edgware Road station explosion, the British Press Association reported.

Clarke said police have identified the suspected suicide bomber on the train between Russell Square and King's Cross -- site of more than half the deaths -- but were not releasing his name. Officials familiar with the investigation said it was Lindsay.

Two-minute silence

Millions in Britain and around the world observed a two-minute silence Thursday to honor the victims of the attacks.

In a massive show of defiance called by London Mayor Ken Livingstone, buses and taxis across the city stopped, airports fell silent and people came out of workplaces and homes onto the streets to remember those who died.

Queen Elizabeth II stood in silence on the forecourt of Buckingham Palace as Big Ben tolled at noon.

In Trafalgar Square, where a vigil later took place, books of condolence were opened for Londoners and visitors to the city to sign. (Tributes and tears)

Tributes also were held in the resort island of Bali, targeted by al Qaeda in 2002, and in the three U.S. locations struck on September 11, 2001 -- New York, Pennsylvania and Washington, D.C. (World remembers)

Search widens

The search for clues widened to include a new address in Leeds and a house in the market town of Aylesbury northwest of the British capital.

Police in Leeds evacuated nearly 200 homes, a mosque and a school in about a square mile near Tanweer's home.

A bomb disposal team truck was spotted in the area. But West Yorkshire police would not give a reason for the evacuation.

Police focused on a home about 200 meters from Tanweer's house. They threw a 100-meter cordon around the area affected by the evacuation and prevented aircraft from flying over the area, police said.

Police were still questioning a 29-year-old man arrested during their initial search in Leeds earlier this week.

Police are searching for what they believe may be a "network" of people who organized the attacks. They want to determine if the four suspects were coached by a master bomber, who may be on the run.

Officials are also looking at the origin of the explosives in the hope that could lead them to the architect of the attacks.

Officers said they feared it could be a senior al Qaeda operative who arrived in the country several months ago and then fled the day before the atrocity, the Press Association reported.

U.S. lead

The FBI is looking into the background of an Egyptian whom British police are seeking in connection with the bombings.

Magdy El-Nashar earned a doctorate in biochemistry from Leeds University this year, the university said.

He also studied chemical engineering at North Carolina State University in Raleigh during the spring semester in 2000, according to the school's records. (Full story)

British police appeal for public's info

Fourth suspect in the bombings identified