Fire crews were called to a building at 71 Daggett Drive around 9 a.m. when someone reported an explosion and fire that left two workers badly burned, Fire Capt. Reggie Williams said.
Williams said three men were working on an electrical unit in the back of the building when it suddenly exploded, causing a small fire.
One of the workers was critically burned in the blast, while another suffered serious burns to the face and hands, the fire captain said.
Both were rushed to a hospital burn center to be treated for their injuries.
The building where the explosion occurred was at one time occupied by science software manufacturer Finesse Solutions, LLC.
Williams said it is unclear whether the company still uses the building, and a spokeswoman for Finesse could not immediately be reached this morning.
Both PG&E crews and personnel from the California Division of Occupational Safety and Health were called to investigate the incident, he said.