(AP) Transportation officials are taking steps to keep airport metal detectors plugged in and end passenger delays that Secretary Norman Y. Mineta called embarrassing.

Brackets and other devices will be used to ensure that the machines remain plugged in.

In an eight-day period, unplugged machines in Birmingham, Ala., Boston, Buffalo, N.Y., Chicago and Los Angeles forced airport terminals to be evacuated and passengers to go through security a second time. Hundreds of flights left late.

"This is an embarrassing kind of thing," Mineta said.

This was not the first time unplugged detectors caused delays and inconvenience. Passengers were delayed for hours at Seattle-Tacoma International Airport in November. A month later, the same problem caused passengers to be evacuated and rescreened in Charlotte, N.C.

The problem is that no one noticed that the plugs had come undone until after passengers went through the checkpoints, said Jim Mitchell, a spokesman for the Transportation Security Administration.

Mitchell said there was no evidence that disgruntled security screeners, who will be replaced by a federal work force later this year, were pulling out the plugs.

Officials are also looking at ways to partition airport concourses so they can limit the number of passengers and flights affected by a security breach, Mineta said.

In Los Angeles, airport security officials had to clear five terminals because passengers could have entered any of them after passing through a checkpoint with an unplugged machine. Some 10,000 passengers had to go through security screening a second time and around 400 flights were delayed.

By Nov. 19, checkpoints are to be staffed by federal workers, except for five airports that serve as pilot programs for different security approaches, including private employees.

The Port Authority of New York and New Jersey has requested such a pilot program for Kennedy Airport. Under the proposal, all the 1,500 to 2,000 security screeners there would be retired law enforcement officers. Many police officers can retire at half pay after 20 years, and proponents say there are thousands of men and women in their 40s eager to begin a second career protecting airline passengers.