JACKSONVILLE, Fla. -- Documents seized from group of 45 Muslim doctors threatening to use car bombings and other attacks in the United States said their first target would be "the naval base that gives shelter to the ship Kenney," The Telegraph of London reported Thursday.

Video: Mayport Named In 2005 Terror Threat

Police found details of Internet discussions in a home in southeast London, the Telegraph said. "We are 45 doctors and we are determined to undertake jihad and take the battle inside America," said one discussion, dated Feb. 12, 2005.

The Telegraph said the post was believed to be a reference to the USS John F. Kennedy, which remains at Mayport Naval Station following its decommissioning in March.

The message discussed targets at the base, including, "clubs for naked women."

The online discussions also referred to using six Chevrolet GT vehicles and three fishing boats and blowing up petrol tanks with rocket propelled grenades.

FBI Special Agent Jeff Wescott said that the agency investigated hundreds of threats in 2006, some of which resulted in criminal charges in four different countries, including the United Kingdom.

"The threat that is referenced in today's published report was thoroughly investigated by the FBI and determined not to be credible," Westcott said.

The Navy's statement was even less specific.

"While we cannot comment on specifics, the Navy continuously monitors and assesses intelligence from a variety of sources, and makes appropriate adjustments to its force protection measures to ensure the security of all Navy personnel and property," Mayport Public Affairs Officer Bill Austin said.

Associate University of North Florida professor and foreign affairs expert Dr. Patrick Plumlee said the possibility of getting inside and carrying out a plot in highly secured area like Mayport is unlikely, but that other targets could not be counted out, which was made evident by last week's terror scare in Great Britain.

"It's just a lot easier to do that closer to home than to try to do it remotely thousands of miles away. That's a huge operation and undertaking, relative to the kind of resources that these groups tend have at the local level," Plumlee said.

British investigators have found no link between the Internet discussions and the doctors and other medical personnel in custody in connection with last week's attempted bombings in London and Glasgow.

The British government on Wednesday lowered its terror threat level, from the highest one -- critical -- to the next-highest, which is severe.

That still means further attacks are considered likely.

The alert status was elevated after the failed attacks in Glasgow and London.

In a statement, Britain's home secretary said there is still a "serious and real threat against the United Kingdom." And she asked the public to "remain vigilant."