California governor reveals threat to bridges.(Knight Ridder Newspapers)

SACRAMENTO, Calif. _ Gov. Gray Davis on Thursday issued a dramatic warning of possible terrorist attacks against four major bridges, including the Golden Gate and Bay bridges, but sought to reassure anxious Californians that heightened security would " ensure their safety."

Davis described the threat, which the FBI transmitted to state officials Wednesday night, as "credible," but federal officials in sharp contrast chose to stress that the information was "unsubstantiated" and less urgent than the national alert issued Monday.

The threats are the most detailed made public in the wake of the Sept. 11 terrorist attacks and the first to suggest that terrorists, possibly tied to Osama bin Laden, might currently be planning attacks on the West Coast.

The FBI advisory, which was sent to law enforcement officials in seven Western states, said the department had "uncorroborated information" that indicates "unspecified groups" planned six rush-hour attacks on West Coast suspension bridges.

"We believe there's a credible threat that there will be an effort made between Nov. 2 and Nov. 7 to destroy those bridges" Davis told a Los Angeles news conference.

Even though the warning ...