South San Francisco Fire Marshal Luis Da Silva told Bay City News the solvents, used to sterilize lab equipment, caused a chemical reaction and flash fire at the biotechnology company's lab at 1120 Veterans Blvd about 3:30 p.m. The workers were being treated at a local hospital.
Da Silva said while the building was evacuated as a precaution, it appeared there was no public health concern.
"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.
A waste-disposal worker was seriously burned while collecting waste at the same facility in May, and Amgen was handed a "serious" citation, the San Jose Mercury News said.