Homeland Security and other U.S. counterterrorism and national-security officials say they know of no specific information indicating that the apparent terror threat in London extends in any way to the United States or is linked to any current plot directed against U.S. targets. “At this point, I have seen no specific, credible information suggesting that this incident is connected to a threat to the homeland,” said Michael Chertoff, the Homeland Security Secretary, in a statement. “We have no plans at this time to change the U.S. threat level. DHS and the FBI have been in touch with our state and local homeland security and law-enforcement partners to convey available information.”

But authorities in New York are taking extra precautions anyway, according to a senior law-enforcement official familiar with current police operations in the city. The official said that New York Police Department officers currently policing the subway system will be held on duty after their shifts normally end on Friday night and that NYPD is also setting up special checkpoints to screen vehicles entering the city, particularly the borough of Manhattan. NYPD is also activating a special operation to use sensors to check parking garages for evidence of possible terrorist activity, including traces of radioactivity or possible chemical weapons. But the official noted these moves are precautionary and not a response to any specific threat directed against New York.

In London, authorities discovered the first bomb at about 1 a.m. last night, London time, when an ambulance crew was called to a nightclub near Piccadilly Circus, one of the British capital’s busiest entertainment districts. The police said the ambulance had gone to the Tiger Tiger club in The Haymarket, Piccadilly, London W1 to treat a person who had been taken ill. But while there, the police said, medical technicians noticed a Mercedes parked outside the club that appeared to have smoke inside it. Ambulance personnel called the police, and when Scotland Yard bomb-disposal experts examined the car, they found what the police described as “significant quantities” of gasoline as well as gas canisters and a large number of nails inside the vehicle. Scotland Yard says its officers “disabled a potential means of detonation of the gas and fuel in the vehicle”; some news reports indicated this was accomplished when a police officer noticed what may have been a cell phone in the car that had been rigged up to trigger the bomb and wrenched it from the device, though this account has not yet been officially confirmed.

Late Friday, Scotland Yard announced that a second, similar bomb had been found and disarmed. Police officials said they discovered that device after ticketing another Mercedes at about 2.30 a.m. It had been parked around the corner from the nightclub where the first booby-trapped Mercedes was found. After being ticketed, the second car was towed to an underground car pound on the edge of Hyde Park, a couple of blocks from the American Embassy.

When police examined the car during the day, they discovered it contained “very similar materials” to what had been found in the first Mercedes, including gasoline, gas canisters and what a police spokesman said was a “substantial quantity of nails.” “The vehicles are clearly linked,” said Peter Clarke, Scotland Yard’s deputy assistant commissioner. London investigators are also wondering whether there’s a connection between the explosive-rigged cars discovered early Friday morning and the change of government in Britain on Wednesday, when Tony Blair resigned as prime minister and was succeeded by Gordon Brown, his chancellor of the Exchequer.

Sources in the United States and Britain told NEWSWEEK that Scotland Yard already is looking for particular suspects in connection with the failed bombings. One official said that authorities were “scouring” the United Kingdom looking for the individuals, who, according to some accounts, may be from Birmingham, England. Authorities acknowledged that they are considering the possibility that the plot was orchestrated by Al Qaeda or local elements inspired by Osama bin Laden’s terror network. Officials could not immediately confirm some news reports indicating that a suspect in the latest plot may have surfaced in a previous terrorist investigation .

Despite some news reports suggesting a possible warning about a London attack had appeared on a known Jihadi Web site, officials in the United States and the United Kingdom told NEWSWEEK they had not confirmed that there had been any specific advance warning of a London attack, nor were there clear intelligence indicators before today that such an attack might be in the works.

But many U.S. and European counterterror officials during the past several weeks have become increasingly anxious about the possibility that terror plots are in the works against U.S. or European targets. One senior German counterterror official said at a press conference last week that he saw parallels between what counterterror officials were seeing in intelligence reporting today and the kind of intelligence reporting authorities saw in the months before the September 11 attacks. U.S. officials have expressed particular concern about indications of possible terror plotting or machinations in tribal areas along the Afghanistan/Pakistan border—the region where Osama bin Laden and what ever else remains of the Al Qaeda high command are believed to be hiding out.

Officials in the United States and Britain said that initial investigations suggest there may be some similarities between the type of homemade but large-scale car bomb discovered in Piccadilly Circus and car-bomb blueprints outlined in materials seized from a now-convicted U.K.-based Al Qaeda operative named Dhiren Barot. Before 9/11, Barot, also known as Esa al-Hindi or Issa al-Britani, visited the United States on the instructions of 9/11 mastermind Khalid Sheikh Mohammed to conduct surveillance for possible attacks on prominent financial buildings in New York, New Jersey and Washington, D.C. Evidence collected by authorities indicated that Barot had explored various elaborate plans for blowing up U.S. financial targets, including driving limos into the basements of the buildings and then detonating the vehicles.