The linear accelerator at Stanford University's SLAC National Accelerator Laboratory in California is shut down and two research labs idled after a fire damaged electrical equipment that helps power the accelerator.
SLAC spokesman Andrew Gordon said on Thursday he didn't know when the accelerator would be back up and running.
SLAC conducts research in high-energy physics and subatomic particles.
Gordon said the fire was confined to a school locker-sized electrical cabinet in a building above the accelerator, which is underground. The cause is under investigation.
There was some minor smoke damage around the cabinet, but the accelerator itself was not damaged.
Gordon said the fire also did not create any threat to the public.
The report came into the Menlo Park Fire Department shortly before 10 p.m. PDT Wednesday from the SLAC National Accelerator Laboratory, with focuses on experimental and theoretical research in advanced physics.
Callers reported heavy black smoke coming from the two-mile long accelerator structure, which runs beneath Interstate Highway 280 in the San Francisco area. Menlo Park Fire Chief Harold Schapelhouman said traffic was affected by the smoke.
Fire crews from several area departments responded to the blaze as teams worked to shut down the affected area of the accelerator, Schapelhouman said in a news release.
"Once that was done, firefighters used 7 large mobile carbon dioxide extinguishing carts, stored on-site, to suppress the fire," he said.
The blaze was brought under control about 10:30 p.m., about 45 minutes after it was reported.
The fire appears to have started in a large electrical switching cabinet, but the fire chief said its cause will be investigated by firefighters and facility officials.
The research center was established in 1962 and houses electron accelerators used for the study of high-energy physics. It's one of 10 Department of Energy Office of Science laboratories and is known for its particle and chemical reaction research.