An arc flash explosion at the Idaho National Laboratory last year has earned a contractor a $60,000 fine from federal regulators. Battelle Energy Alliance (BEA) has also been ordered to make safety improvements.

According to news sources, the April 23 arc flash incident was triggered by three BEA workers as they performed maintenance on a circuit breaker. All three were knocked to the ground, but were uninjured.

A letter from the Department of Energy to the lab cited deficiencies in BEA’s hazard identification and assessment procedure, electrical safety program, protective equipment selection process, hazard prevention and abatement procedure, and safety training program.

The DOE said the explosion could have been prevented.