LOS ANGELES >> All container terminals at the Port of Los Angeles have been closed for precautionary reasons over concerns about air quality from a stubborn fire that is sending up a huge plume of smoke.

Port spokesman Philip Stansfield said the eight terminals will likely remain closed until the night shift begins about 5 p.m. Tuesday. He estimated that a few thousand employees, mostly longshore workers, were sent home.

Thick smoke from the fire prompted fire and police officials to urge nearby residents to remain indoors.

The blaze, sparked by a welder’s torch, forced about 850 people to evacuate when it was sparked Monday night.

Fire Chief Ralph Terrazas said while the bulk of the fire is under control, it could take until Tuesday evening for crews to fully extinguish the blaze.

“This is a very, very difficult fire to fight,” he said.

It continued to smolder among the wooden pier timbers, which were coated with water-resistant, highly flammable creosote, a byproduct of the coal industry that is used to prevent erosion.

Thick smoke from the fire prompted the Los Angeles fire and police officials to issue advisories to residents in Wilmington, San Pedro and Long Beach to remain indoors and keep windows closed. Nearby schools remained open with all outdoor activities suspended.

The Port of Los Angeles, along with its twin port in Long Beach, handles 40 percent of America’s import trade. The fire shut down the wharf but was not immediately affecting overall operations at the port, officials said.

More than 150 firefighters had control of the fire about 2 1/2 hours after it broke out Monday night, but stubborn flames underneath the docks proved hard to reach. The fire burned under a warehouse with large metal coils inside. It was contained to about 150 feet of the dock.

Crews attacked the blaze with helicopters and trucks, but fireboats were more effective, and divers in the water helped direct them, fire spokeswoman Katherine Main said late Monday.

Smoke reached two terminals, forcing the evacuation of about 850 workers. No injuries were reported.

Terrazas said investigators determined the blaze was started during a welding operation.

The wharf, which dates to before World War II, is in San Pedro Bay in the Wilmington neighborhood, approximately 20 miles south of downtown Los Angeles.