A stretch of the 110 Freeway in Wilmington remained shut down today because of a rubbish fire that broke out in a tunnel below and created what authorities continued to call an unsafe situation.

The fire was reported at 7:50 p.m. Monday in what was described as an access portal beneath the freeway between Harry Bridges Boulevard and Channel Street, near San Pedro and the Port of Los Angeles.

“This is a complex, prolonged-duration emergency that will have many phases prior to completion,” the Los Angeles Fire Department, Caltrans and the California Highway Patrol said in a joint statement.

The fire is believed to have been started by people living in a homeless encampment. LAFD Heavy Rescue and Urban Search and Rescue crews responded to the northbound freeway where they found the remnants of a fire, LAFD spokeswoman Lyndsey Lantz said.

By 8:50 p.m. Monday, crews were working to access and suppress fire inside the confined space.

A Caltrans highway engineer was called in and LAFD Incident Command was prioritizing firefighter safety while working to extinguish the fire during the operation, Lantz said.

At 10:49 p.m. Monday, the California Highway Patrol said it shut down the 110 Freeway in both directions. Southbound lanes were reopened around 10:30 a.m. Tuesday, but northbound lanes remained closed between Harry Bridges Boulevard and Channel Street.

No injuries have been reported.

“While firefighters have removed a large amount of debris from the tunnel, burning construction timber and other unmovable materials will require sustained suppression,” Lantz said. “Crews are prepared for an extended operation.”

By Tuesday afternoon, the fire was still burning in the tunnel, which is at least 150 feet long.

An LAFD spokesman at the scene said crews had not been able to get in deep enough to find the seat of the fire, which was sending smoke out of the tunnel opening long after the blaze was first reported.

LAFD Assistant Chief Carlos Calvillo told ABC 7 his department is worried about the structural integrity of the freeway after it was assessed by a structural engineer from Caltrans.

A Caltrans official at the location said crews were trying to see if the fire affected concrete, rebar and girders above the tunnel, or if the span can support traffic.

There was no immediate estimate of when northbound lanes would reopen.

“Our aim is to open the lanes as early as we can. Our aim is tomorrow,” Caltrans spokeswoman Lauren Wonder said at a Tuesday afternoon news conference.

Authorities are recommending that drivers take alternate routes.