A frantic 911 call came in around 11:21 a.m. from a plant at 6 Berkeley Road off Lancaster Avenue which houses Environex, an industrial testing lab that uses hazardous materials.
A small blast occurred inside the building and a thin, yellowish smoke drifted from inside.
"The only information we had was that there was a fire in the building. They weren't sure if there was a fire or how big it was," said Capt. Eamon Brazunas of the Berwyn Fire Company.
HAZMAT specialists from Chester County were called. They were concerned because Environex uses highly combustible hydrogen and toxic phosphorus tri-fluoride.
The good news is that neither material leaked.
Scores of firefighters with air packs chased down small fires trapped inside the wall cavities.
Environex would not say what occurred prior to the blast. The Chester County fire marshal's office is investigating.
Two firefighters were treated at the scene for dehydration while one person, apparently a lab worker, was taken to Paoli Hospital with burns to the hands.
