UPDATE: CHP announced just before 6:30 p.m. SB I-805 lanes 1-4 are reopened. Lane 5 and the onramp to Plaza Blvd. was still closed.
SAN DIEGO - A Sig Alert was issued after a tractor-trailer truck hit a mattress on Interstate 805 and caught fire.
Crews closed the 3, 4, and 5 lanes on the southbound side of I-805, as well as the onramp to Plaza Boulevard.
Three lanes of SB I-805 at Plaza Blvd are closed due to a semi-truck fire. Motorists are asked to avoid the area if possible.
— Caltrans San Diego (@SDCaltrans) January 10, 2017
As of 5 p.m., Caltrans said they hope to have the scene cleared by 6:30 p.m. Traffic on the southbound side of I-805 was backed up to University City.
The truck's cabin erupted into flames just before 2 p.m. after it struck a mattress, according to the California Highway Patrol. The fire sparked underneath the driver side of the truck's cabin first, before the rest of the trailer became engulfed in flames.
The trailer was completely destroyed, according to CHP. The driver was able to make it out of the vehicle.
Hazmat crews were called to the scene to cleanup any fuel that leaked from the truck just before 2:30 p.m. An unknown amount of fuel did make it into a nearby storm drain along with water used to put out the fire, according to CHP.
Police advised motorist to avoid the area.
A nearby overpass was also inspected for possible structural damage from the fire.
This is a developing story.