A Sylmar off-ramp from the 5 Freeway was closed Sunday while police and firefighters dealt with a truck with illegal fireworks inside, authorities said.
The investigation began at about 3:30 p.m. in a gas station in the 15000 block of West Roxford Street, said Sgt. Scott Spackman of the Los Angeles Police Department's Mission Station.
The LAPD Bomb Squad with help from Los Angeles firefighters are investigating the situation, Spackman said.
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The truck contains "a large quantity of illegal fireworks," Erik Scott of the Los Angeles Fire Department said.
Police evacuated the gas station and businesses within a minimum of 300 feet, Spackman said. That could include McDonald's and Denny's restaurants and two motels.
Someone has been detained in connection with the fireworks, he said.
The California Highway Patrol issued a SigAlert shutting down the Roxford Street off-ramp from the northbound Golden State Freeway.
"First responders remind the public that all fireworks, even the so- called 'safe and sane' variety remain illegal in the City of Los Angeles," Scott said.