Los Angeles ? The discovery of an unplugged metal detector forced the evacuation of five terminals at Los Angeles International Airport early Thursday and delayed more than 300 flights, authorities said.

Hundreds of passengers from terminals No. 4 through 8 had to be rescreened at security checkpoints after authorities discovered at 6:30 a.m. that a metal detector was not working at Terminal 4, said Federal Aviation Administration spokesman Jerry Snyder.

“One of the metal detectors was found unplugged,” Snyder said. “We do not know if it was malicious or not.”

The five terminals, on the airport’s south side, were emptied as a precaution because travelers could wander between the buildings once they cleared security, airport officials said.

Passengers jammed the sidewalks outside the terminals and began the rescreening at about 8:20 a.m., LAX spokesman Harold Johnson said.

About 325 departing flights from several major airlines, including American, Delta, United and Continental were delayed, he said.

American Airlines spokesman John Hopkins said passengers should expect flight delays of up to several hours.

It was one of several cases of airport problems involving metal detectors reported this week.

On Tuesday, about 500 airline passengers in Buffalo (N.Y.) Niagara International Airport had to be rescreened after a metal detector was found partially unplugged. Ten flights were delayed.

On Monday, a terminal at Boston’s Logan International Airport was evacuated and more than 1,200 passengers rescreened after officials discovered a detector hadn’t been working for up to five minutes.

And not long after the Winter Olylmpics wrapped up late Sunday, flights at Salt Lake City’s airport were held up because a metal detector was found not to have been working and some passengers required rescreening.