SUNOL -- A trucker was airlifted to a hospital with significant burns to his hands, face and legs after the cab of his big rig caught fire on Interstate-680 Thursday night, authorities said.

The California Highway Patrol reported that the man's pants were on fire as he escaped the burning cab. His name and age were not released and his condition was not immediately available.

The rig caught fire about 8:15 p.m. Thursday and was on the right shoulder of the freeway when the CHP arrived, a spokesman said. The fire charred the cab of the rig and spread to a quarter-acre of grass, the spokesman said.

No other injuries were reported.

The two right lanes on I-680 north Sheridan Road are closed, the spokesman said. CHP officials issued a traffic alert for the area, but did not estimate when the lanes would be reopened.

Alameda County Fire spokeswoman Aisha Knowles said one county engine is on scene with CalFire and Fremont Fire.

Check back for updates.

Contact Kristin J. Bender at kbender@bayareanewsgroup.com. Follow her at Twitter.com/kjbender.