London Police Foil Major Terror Plot

A British police officer stands at the cordoned off junction of Coventry Street and Haymarket in central London as police officers investigate a "potentially viable explosive device" Friday June 29, 2007. Explosives officers on Friday dealt with a suspected bomb in a vehicle parked near Picadilly Circus in central London, making it "safe," police said. (AP Photo/Clara Molden/PA Wire) (Clara Molden - AP)

Professor Paul Wilkinson, chairman of the Center for the Study of Terrorism and political violence at St. Andrews University, said a number of factors could have come together to prompt the thwarted attacks.

"With the change in prime minister this could be the work of al-Qaida," he said. "They have a track record of trying to influence political change through violent means such as in the Madrid train attacks.

After the first bomb was announced, a sober Brown said "we face a serious and continuous security threat in our country."

British authorities and White House press secretary Tony Snow were cautious.

"Look, it's terrorism, but we don't know if there _ there's no definite, there's no established connection with any organization at this point," Snow said. U.S. authorities said there was no apparent terror threat to the United States.

There had been no prior intelligence of planned attacks from the terror organization, a British government official told The Associated Press earlier Friday on condition of anonymity because of the sensitivity of the investigation.

The July 7 bombers were all Muslims raised in Britain. A government account of the attacks released last year said it was unclear whether others in Britain had radicalized or incited the group, and that it was not known if al-Qaida figures, or others, had assisted in planning the bombing.

The events unfolded when police were called to Haymarket, south of Piccadilly Circus, after a man fell at the nightclub Tiger Tiger, injuring his head, prompting a call for an ambulance around 1:30 a.m. Friday.

When crews arrived, they noticed smoke coming from a green Mercedes parked in front of a club, Clarke said.

Photographs showed a canister bearing the words "patio gas," indicating it was propane, next to the car. The propane gas is of the type usually used in backyard barbecues and patio heaters. The back door was open with blankets spilling out. The car was removed from the scene after a bomb squad disabled the explosives.

A bomb squad called to the scene manually disabled the explosives.

Sky News television reported that a police officer seized a telephone from the car _ believed to have been a potential detonator for the explosives _ and an American lawmaker briefed on the investigation confirmed that British authorities found a cell phone.