With public transit systems on heightened terrorist alert following the London subway bombings, authorities in the US city of Los Angeles took no chances Saturday when a suspicious object was found at a subway station.

The object, a cooler with wires sticking out of it, was found by a police officer on patrol about 1:20 p.m. local time at the Metro Red Line station in Hollywood, said Los Angeles County sheriff's Lt. John Baylis.

Police officers, firefighters and a bomb squad were called, while two subway stations were evacuated and nearby streets closed.

"We had about 120 to 150 people down there at the time because a train had just come in," Bill Heard of the Metropolitan Transportation Authority told a local TV station. "We got everybody up to the surface in good order."

After the cooler was spotted by a deputy, it took well over an hour for the bomb squad to arrive at the subway station, Baylis said, adding that the bomb squad was held up by traffic.

Once the specialists were on scene, it took about 20 minutes for them to X-ray the cooler and determine it was empty, he said.

The stations and streets were reopened later about 3:30 p.m.

Authorities said it wasn't clear who placed the suspicious-looking cooler in the subway tunnel, or why.

The incident was treated with the same level of precaution the L.A. Police Department treats all such incidents, regardless of the bombings in London on Thursday, Baylis said.

He said the terrorist early warning system is in use, and that the incident will be reported to state and federal investigators.

"Whether it's an orange or a red alert, all situations like this are handled appropriately," he said.