U.S. won't dismiss possible July 4 plot

WASHINGTON (CNN) -- Islamic terrorists may be plotting an attack on a nuclear power plant around July 4, according to information passed to the United States by a foreign intelligence service.

While officials stressed the information may not be reliable, they said they're not dismissing it either.

The intelligence report led to the posting of a recent alert to U.S. nuclear power plants and FBI counterterrorism units to be watchful for people who might be photographing or doing surveillance of key facilities.

The information comes from an unnamed foreign intelligence service that has not always been accurate in the past, an official said.

CNN NewsPass VIDEO U.S. officials receive word that Islamic terrorists may be planning an attack on a nuclear power plant around July 4th. CNN's David Ensor reports (May 13) Play video   RESOURCES Map of nuclear reactor sites in the United States

Defense Secretary Donald Rumsfeld declined Monday to say how much credibility he places in the report.

"I don't discuss intelligence, to confirm it or to deny it," he told reporters.

U.S. officials earlier confirmed that Abu Zubaydah, the senior al Qaeda prisoner, has told American interrogators at least two al Qaeda operatives in the United States were planning to build a radiological bomb -- a conventional bomb laced with radioactive material to heighten panic. Zubaydah suggested the material would be obtained in the United States.

Officials say this latest report about a July 4 threat to a nuclear power plant did not come from him.

The existence of the July 4 threat information was first reported by The Washington Times, which said an unidentified Islamic terrorist group was planning to attack Three Mile Island nuclear facility in Pennsylvania or another one in the United States.

U.S. officials say no particular facility is named in the threat information from the foreign intelligence service.