(Updates with some freeway lanes reopened)
LOS ANGELES, April 25 (Reuters) - Two big rigs and several cars collided on a freeway north of downtown Los Angeles on Tuesday, sparking an explosion and fire, killing at least one person and forcing authorities to shut down two major arteries into the city for hours.
Several other people were injured in the fiery crash, which sent plumes of thick black smoke billowing into the sky, said Officer Kevin Tao of the California Highway Patrol. The Los Angeles Times reported that nine people were hurt.
Local television images showed firefighters pouring water on the burned-out hulk of a tanker truck, a small car wedged underneath. A black pick-up truck that had been towing a trailer had come to rest on top of a center median, it's rear wheels well off the ground.
Local KTLA-TV reported that drivers not involved in the wreck fled their cars, running off the freeway onto a nearby golf course to escape the flames and carnage.
The crash, which took place shortly before 11 a.m. local time, prompted authorities to close Interstate 5 in both directions north of downtown Los Angeles and the resulting clean-up and investigation also jammed the Ventura (134) Freeway and nearby surface streets.
The northbound side of I-5 were reopened several hours later but southbound lanes were expected to remain closed through the evening rush hour, the CHP said.
"We're advising motorists to try to avoid the area as much as possible," Tao said. "They may have to find alternate routes. Be patient with us, we're doing our best to get the lanes opened up as soon as possible." (Reporting by Dan Whitcomb; Editing by Chris Reese and Andrew Hay)