Two contractors at a Bay Area refinery are in the hospital after they were injured in an acid incident. 

Officials at the Tesoro Corporation refinery near Martinez say the contractors were doing maintenance work Monday morning when they were splashed with sulfuric acid. 

Both workers suffered injuries despite wearing protective gear, and were taken to the hospital with burns. 

A Cal-OSHA spokesperson says the incident involved the same pipes where two workers were burned by acid last month. 

It's unclear what exactly went wrong Monday that caused the contractors to be sprayed.