Fire crews were dispatched to the South San Francisco biotechnology company just after the incident was reported around 3:30 p.m. at 1120 Veterans Blvd., South San Francisco Fire Marshal Luis Da Silva said.
Da Silva said he did not know the severity of the injuries to the lab workers, but said that some cleaning solvents used to sterilize equipment caused a chemical reaction that spawned a flash fire.
The Amgen building was evacuated while crews tended to the victims and assessed the danger. Da Silva said it was determined that no chemicals were released into the atmosphere and that there was no public health concern as a result of the incident.
The explosion prompted a second-alarm response, and more than 10 fire apparatus from throughout San Mateo County arrived at the scene and police controlled traffic.
A section of Oyster Point was closed between Gateway and Veterans boulevards. It has since been reopened, but traffic turning onto Veterans Boulevard from Oyster Point Boulevard is being detoured, Da Silva said.
"It's all winding down now, we are now going through the steps and making sure everything is OK and that there are no other issues or hazards present," he said.