Terrorists may have targeted the Palo Verde nuclear power plant in Arizona, Energy Secretary Spencer Abraham said Thursday. Arizona Gov. Janet Napolitano has sent National Guard troops to provide additional security at the plant.

Abraham told members of the Senate Armed Services Committee during a hearing that he couldn't go into details about intelligence reports concerning the plant, the nation's largest commercial nuclear power facility. The plant near Phoenix consists of three commercial power reactors.

But in response to a question by Sen. John McCain, R-Ariz., he acknowledged there were indications that it might have become a target for terrorists.

"Actions are being taken by all the appropriate agencies to address the concerns that have been raised," Abraham said.

Homeland Security Department chief Tom Ridge, testifying separately on Capitol Hill, said there had been no reports of incidents since the bombing of Iraq commenced Wednesday night.

He said there had been an additional layer of security in place around the country since Monday when the department raised the national terror alert to orange, indicating a high risk of attack. There are no immediate plans to change that alert level, he said.

The Washington Times, citing intelligence reports distributed to law enforcement officials, reported Thursday that the government is looking for Iraqi "sleeper cells" that might have planned an attack on the Palo Verde plant near Phoenix.

McCain said while he had not been able to get any more derails about the threat involving the Palo Verde plant, he has been told "there is an increased threat all over the country" as reflected by the upgrading of the security level to Code Orange.

Jim McDonald, a spokesman for Arizona Public Service Co., said the guardsmen are augmenting the utility's own beefed-up security force at the plant, located on 4,000 acres 50 miles west of downtown Phoenix.

"We have taken steps to fully protect the plant and our ability to continue to operate it safely," McDonald said in a telephone interview. "We don't think there is anything we can't deal with."

The Transportation Security Administration sent a security directive to airports and airlines Tuesday night, telling them to post more law enforcement officers in and around terminals and airport perimeters. Some airports were ordered to conduct random vehicle inspections. Some restricted parking in lots close to terminals.

Sen. Olympia Snowe, R-Maine, criticized the TSA for failing to communicate quickly with key law enforcement officials the last time the terrorism threat alert was raised. This time, her office checked and found the people most involved with homeland security had learned in advance about the Monday night decision to go to code orange, the second highest level.

"It's getting better," said Snowe's spokesman, Davis Lackey. "They've worked through the initial delays."

The Coast Guard is now escorting ships into port and stepping up patrols of waterways. Four special maritime security units of 100 Coast Guardsmen each are in position in undisclosed ports.

Pipeline operators were advised by the Transportation Department to take a series of actions to protect the 2.3 million miles of pipe within the United States. At code orange, the pipeline industry has a checklist of 44 more things to do, such as posting security at critical points 24 hours a day.

The Federal Transit Administration, which has been conducting emergency forums with transit systems since Sept. 11, advises them to move cars and trash containers away from buildings, make sure their intruder alarms are working and disable baggage lockers.