Edison Mission spokesman Charley Parnell says a 6-inch-high pressure steam pipe ruptured around 7:45 a.m. Thursday at the coal-fired plant in Homer City, about 40 miles east of Pittsburgh.
Three workers were flown to a hospital burn unit. There was no word on their conditions. The other three were treated at local hospitals and two of them released.
Parnell says the plant was evacuated and all employees accounted for.
He says an investigation into the cause of the blast is under way.