The area where a blaze forced the closure of lanes of the 405 Freeway through the San Fernando Valley on Wednesday was being investigated as a crime scene, the California Highway Patrol said.

Several people of interest were detained, then cleared in connection with the fire that burned trees along embankments of the 405 and 118 freeways in Mission Hills, arson investigators said.

Fire officials were working to determine what set off the blaze and whether it started at a homeless encampment near the freeway.

Aerial footage showed cars traveling through heavy smoke as it billowed from the sides of the 405 Freeway. The fire grew to three acres as strong gusts spread embers across the area, the Los Angeles Fire Department said.

The CHP began opening lanes after the fire was knocked down about 4:30 p.m. Three northbound lanes were reopened, along with two southbound lanes.

No structures were threatened, fire officials said, though towering flames could be seen consuming trees across the street from homes. A helicopter made water drops as crews on the ground doused hot spots.

The fire broke out as record-high temperatures were expected during another round of hot, dry and windy weather. Red-flag warnings were in effect for most of Southern California, where several wildfires broke out Wednesday north of San Diego.

Rosa Ordaz and Gadi Schwartz contributed to this report.