D.C. Boosts Security For Holiday Festivities

British police discovered a car rigged with gas-cylinder bombs near a London nightclub Friday after an ambulance crew on an unrelated call reported smoke in the vehicle. A second, similar car was found in the area hours later. In the third attempt, two men rammed a flaming Jeep into a terminal at Glasgow Airport on Saturday.

In recent days, D.C. police have been contacting local businesses, asking them to report unusual sales of propane tanks, fertilizer or other materials that could be used to make crude bombs such as those used in Britain, Lanier said.

"We do not have a specific heightened threat" for today, Joseph Persichini Jr., head of the FBI's Washington field office, said at a news conference held with local and federal law enforcement officials.

But he called on businesses to notify authorities about "individuals who may be buying propane, gasoline" in unusual quantities.

Since Friday, federal officials have issued several intelligence assessments of the London and Glasgow incidents and the potential threat of an Independence Day attack in the United States. One update included a list of about 10 large vehicle-bomb indicators, such as size, weight and unusual odors, one U.S. counterterrorism official said.

Homeland Security Secretary Michael Chertoff has noted the similarity of the bomb attempts in Britain to a "Gas Limos Project" uncovered in July 2004. The plot involved Dhiren Barot, an al-Qaeda operative and British citizen who had cased targets in New York, Newark and Washington. Another British investigation, Operation Crevice, disrupted a 2004 plot to bomb a London nightclub, power plants and a shopping mall.

"The thing in the United Kingdom we saw was very similar to what Barot planned, and the fact that he was here in the U.S. concerns us, and what he surveiled and targeted concerns us," said Michael Downing, deputy chief of the Los Angeles Police Department.

Teams of TSA screeners, inspectors and air marshals were dispatched early yesterday to begin patrolling the Metro, Union Station and Reagan National Airport.

Members of the squads -- known as Visible Intermodal Protection and Response teams -- are trained to spot suspicious behavior and often work with explosive-sniffing dogs, officials said. Some members are in uniform, and others wear plain clothes to blend into crowds.

TSA officials said they had planned to deploy the teams in the D.C. area as part of their normal response to the Fourth of July festivities, as they did last year. But they increased the number of patrols in response to the London incidents, officials said.

Additional security measures could include random vehicle searches on airport approach roads, said Jonathan Dean, spokesman for Baltimore-Washington International Thurgood Marshall Airport.

Hawley said the TSA is experimenting with the size of its patrols, boosting some to as many as 40 people.