WASHINGTON (AP) Inspections in the past week at seven of the nation's 20 highest-risk airports found most airlines are not complying with new federal orders to scan all checked baggage for explosives, the Transportation Department's inspector general said Thursday.

The Federal Aviation Administration directed the airlines in a previously undisclosed order after the Sept. 11 airliner hijackings to make continuous rather than part-time use of their high-tech bomb-detection machines.

"Despite a recognized need for heightened security, air carriers still are not fully utilizing these machines to the maximum extent possible," Transportation Inspector General Kenneth M. Mead told a House aviation subcommittee hearing.

At the FAA's request, Mead would not disclose which airports or airlines were inspected. But last week, acting Massachusetts Gov. Jane Swift reassigned the head of security at Boston's Logan Airport, where two of the hijacked airliners departed.

FAA Administrator Jane Garvey said in an interview Thursday she had just learned of the inspector general's findings and needed to examine them further.

"We need to know more about it," she said. "There's also a question ... if the term 'continuous' is too ambiguous. We have required that it be continuous and we are enforcing it."

A spokesman for the Air Transport Association, a trade group for the airlines, disputed the inspector general's finding Thursday.

"Our carriers are doing what they are instructed to do by the FAA," Michael Wascom said.

Officials told the subcommittee that before last month's FAA order, the million-dollar-plus bomb detection machines were used only selectively largely based on responses to a computer-assisted passenger profiling system and for passengers lacking proper IDs or failing a security quiz.

The FAA has spent $441 million for 164 of the machines, most of which were installed at almost 50 airports for use by 20 airlines. About 20 machines remain in a warehouse and are to be put to use in coming months.

James F. O'Bryon, deputy director of the Pentagon's live fire testing program, said FAA security chief Michael A. Canavan had told him Wednesday the machines must test for nearly 100 different types of explosives.

The subcommittee's chairman, Rep. John Mica, R-Fla., accused the FAA of being "negligent" in failing to utilize the best aviation security technology.

"The public would be shocked to find out how few of the new weapon detection machines have been operating at our nation's airports," he said. "But perhaps the most outrageous finding is the fact that of the machines that are at the airports, they have been used only a fraction of the time."

Before the terrorist attacks, the bomb detection machines went mostly unused, Mead said. In July, the latest month for which figures are available, the machines screened an average of only 350 bags per day, well below their capacity to screen 150 bags an hour, he said.

"Air carriers' reluctance to increase the use is centered in their belief that passengers would not accept the inconvenience," Mead said.