A big rig fire on the northbound 5 Freeway north of Castaic blocked multiple lanes Thursday afternoon, officials said.

UPDATE: As of 4:45 p.m. Thursday, the SIG Alert that was issued due to the big rig fire has been lifted, according to officials with California Highway Patrol.

Just before 3 p.m. Thursday, firefighters received reports of a brush fire on the northbound 5 Freeway near Templin Highway, said Brian Stephens, an inspector with the Los Angeles County Fire Department.

However, when units arrived at the scene, they advised there was no brush fire, according to officials.

“It was a (big rig) with flames underneath the vehicle,” Stephens said. “There was no spread to the brush.”

The California Highway Patrol has issued a SigAlert closing the No. 2, 3 and 4 lanes until approximately 5 p.m.

Traffic is backed up from Lake Hughes Road as of Thursday afternoon, according to officials.

Ed. Note: This is a breaking news story, more information will be added as it is available.

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