"That was the initial report from the school. It's speculation," Gonzales said.
Gonzales said the school district said the classroom had not been used since the 6.0-magnitude Aug. 24 South Napa earthquake.
In an email this morning, the Vallejo City Unified School District said the blast happened in a classroom that was under construction and no students were in the immediate vicinity.
District officials did not return calls for further comment this morning.
Vallejo Firefighters said on a Facebook post the explosion happened in a computer/photo lab.
The employees were performing maintenance duties at the time of the 8:20 a.m. explosion and they were taken to local hospitals, Vallejo firefighters said in the post.
There were no students inside the high school at the time and no students were injured, firefighters and school officials said.
The school at 840 Nebraska St. was given an all-clear and classes resumed this morning, the school district said.
The dangers have been isolated and mitigated, classes have resumed and the cause of the fire is under investigation, firefighters said.