LIVERMORE, Calif. -- An operational emergency has been declared at the Lawrence Livermore National Laboratory as the result of a grass fire that has burned about 7,000 acres near the lab's test facility, lab officials report.

The fire, which was reported around 4:30 p.m. near Greenville and Tesla roads, is not threatening any structures, according to the lab.

An operational emergency is declared when an event occurs that requires mutual aid assistance from agencies outside the laboratory but does not involve the release of hazardous materials. Tuesday's operational emergency was declared around 5:45 p.m., according to lab officials.

The fire is expected to burn all night and is headed in the direction of Interstate 5.

Firefighters are having problems battling the fire because of the high tension power lines in the area.

No evacuations have been called for and no injuries have been reported.

Agencies including the California Department of Forestry and Fire Protection, Alameda County Fire Central, and the fire departments of Livermore-Pleasanton, Tracy and San Joaquin County have responded.