A big rig overturned on the 605 Freeway early Tuesday morning, prompting an hourslong closure for the southbound lanes of traffic through the Avocado Heights area.

The crash between the big rig and a passenger vehicle was reported about 1:42 a.m. near the 60 Freeway, California Highway Patrol Officer Tony Polizzi said.

Fuel spilled out of the overturned big rig, prompting a Sigalert for the closure of all southbound lanes.

Traffic was being taken off the freeway at Valley Boulevard.

Big rig driver Larry Adams said he was travelling from the high desert to South Gate with a load of limestone when he felt his truck begin to fishtail.

“I almost went over the bridge so … you think about your family when it happens,” Adams said.

Both drivers appeared to be OK following the crash and refused emergency transport to a hospital.

An officer at the scene said the driver of the passenger vehicle involved in the crash may have fallen asleep but the official cause of the crash is still under investigation.

The freeway closure snarled traffic through the area for morning commuters.

The lanes were reopened to drivers about 7:45 a.m.