A firefighter knocks down hot spots on the remains of an unoccupied single-wide trailer used as a residence by the state park rangers on Corral Hollow Road
A firefighter knocks down hot spots on the remains of an unoccupied single-wide trailer used as a residence by the state park rangers on Corral Hollow Road across from Carnegie State Vehicular Recreation Area between Livermore and Tracy, Calif., on Wednesday, July 31, 2013. A 5-acre grass fire that started on Lawrence Livermore National Laboratory's Site 300 land spread to the structure. Cal Fire and Alameda County Fire Department units responded to the fire. (Doug Duran/Bay Area News Group)

LIVERMORE -- A firefighter was injured and a mobile home was destroyed during a 20-acre vegetation fire on Lawrence Livermore Lab property Wednesday afternoon, a spokeswoman for the Alameda County Fire Department said.

The two-alarm blaze began at 3:51 p.m. off West Corral Hollow Road and was contained about 6 p.m. said Alameda County fire spokeswoman Aisha Knowles.

Crews remained on the scene for several hours checking for hot spots and flare ups, she said.

The fire was at least one mile away from Lawrence Livermore National Laboratory's Site 300, an experimental test site, Knowles said.

Firefighters from CalFire, Camp Parks Fire Department assisted Alameda County Fire crews, along with firefighters from the Livermore-Pleasanton Fire Department.

The cause of the fire is under investigation.

Staff writer Katie Nelson contributed to this report. Contact Kristin J. Bender at kbender@bayareanewsgroup.com. Follow her at Twitter.com/kjbender.