As Britain Pursues Suspects, America Increases Security

British authorities are hot in pursuit of suspects connected to three attempted terrorist attacks in the United Kingdom.

Authorities captured two more people today in connection with Friday's failed car bombs in London and Saturday's attack on Glasgow airport, bringing the total number of suspects in custody to seven.

This weekend, two suspects were captured at Glasgow airport, where a flaming Jeep Cherokee was driven into the airport's main terminal Saturday.

One of the suspects, who suffered severe burns after the attack, was taken to the nearby Royal Alexandra Hospital.

Police also arrested a 26-year-old man in Liverpool, and captured another man and woman speeding down a highway in northern England. One of those two has been identified as Mohammed Asha, a 26-year-old doctor who worked at a hospital in North Staffordshire. The woman arrested with him was believed to be his wife.

Investigators now believe all the plotters are foreigners of several Middle Eastern nationalities. They say the bombers were likely motivated by al Qaeda, but still have not established an operational link.

Police have established clear links between the attack in Glasgow Saturday and the failed car bombs in London Friday: Explosive devices containing gasoline and propane tanks were used in both incidents.

Sunday afternoon, police carried out a controlled explosion on a car parked near the Royal Alexandra Hospital. They said the vehicle might also be connected to the foiled attack.

According to a statement released by the Strathclyde Police, there was "no indication that the vehicle contained any explosives, however, as a precautionary measure … a controlled explosion was carried out."

ABC producer Matt McGarry reported hearing "several controlled explosions at the Royal Alexandra Hospital" in Glasgow.

"But," he said, "explosion is a misnomer, and police didn't actually 'blow up' the suspicious vehicle."

"It sounded much more like the pop of a shotgun blast," he said. "They were most likely just small detonations designed to set off any larger suspected bomb, which could be in the vehicle."

Britain remains at its highest terror alert. Outside of airports and train stations, police are stopping drivers to search their cars with sniffer dogs. The Wimbledon tennis tournament is also under increased security.

"We are facing the most serious threat and sustained threat from terrorism and in particular al Qaeda-related terrorism," Home Secretary Jacqui Smith said.

Attack Planned in America?

America could see a similar increase in security. Brian Ross, ABC News' chief investigative correspondent, reported today that a classified U.S. law enforcement document predicted that a "terrorist spectacular" was being planned this summer by al Qaeda.

But on "Good Morning America," Homeland Security Secretary Michael Chertoff said the government had no evidence that an attack was being planned against the United States.

"We do not have any specific, credible information about an attack directed at the United States and we didn't have any specific, credible information about an imminent attack in Glasgow," he said.

Chertoff said Americans might see more security as the Fourth of July approached, but that doesn't mean the country is expecting an attack anytime soon.

"We have taken steps to implement preexisting plans to increase security at our airports, at our mass transit and other transportation centers," he said. "That is partly a reflection of what happened over the last few days and partly a recognition of the fact that, during a heavy travel period, there will be crowds and we want to take extra precautions. Again, [there is] no specific threat that we are aware of at this point."