Three employees were injured in an explosion Wednesday at a tank cleaning facility in East Chicago, Indiana.

The explosion was reported at 7:22 a.m. in the garage area of T.A.C. East, 200 E. Gary Road in East Chicago, according to East Chicago Fire Chief Anthony Serna.

Five employees were in the garage at the time, and three of them suffered first-, second- or third-degree burns to their arms and hands, Serna said. They were taken to Methodist Hospital Northlake Campus in Gary, Indiana. Two of them were later transferred to Chicago-area hospitals.

Investigators from the Indiana Fire Marshal’s office and the East Chicago Fire Department are working to determine the cause of the explosion, Serna said. Initial reports indicated the fire started with a boiler explosion, but further investigation revealed it may have involved the company’s tank cleaning process for cleaning tanks used to haul fuel or other chemicals.

The fire spread from the garage to an attached two-story office building, according to Segura. The blaze in the garage was extinguished by 11:30 a.m., but crews are still working to put out the office building fire.