A major road near the centre of Los Angeles was closed as a massive fire ravaged land underneath it.

The fire sent towering flames into the night sky in the early hours of Saturday. Dawn revealed twisted guardrails and blackened, chipped concrete at an Interstate 10 overpass in an industrial zone.

The California Department of Transportation sent personnel to inspect the road, with diversions set up to ease snarled up traffic.

The affected part of Interstate 10, which runs east-west, was expected to be closed for at least 24 hours, authorities said.

Democratic governor Gavin Newsom declared a state of emergency and directed the state Department of Transportation to request assistance from the federal government.

“The state is mobilising resources and taking steps to ensure any necessary repairs are completed as soon as possible to minimise the impact on those travelling in and around Los Angeles,” MR Newsom said.

The cause of the fire has not been disclosed.

The fire department said the blaze burned through trailers, wood pallets and other things in storage areas under both sides of the road, though firefighters successfully safeguarded three nearby commercial buildings.

More than 160 firefighters from 26 companies responded to the blaze, which spread across eight acres and burned parked cars and damaged a support for high-tension power lines.

Fire department spokeswoman Margaret Stewart said no injuries from the fire had been reported.