The derailment occurred at about 8 a.m. in Vandergrift, a small town 30 miles northeast of Pittsburgh, WTAE-TV, Pittsburgh, reported. Authorities said 19 cars loaded with crude oil and two with propane from the 120-car train left the tracks.
Dan Stevens, a spokesman for Westmoreland County, said no injuries were reported. A building at MSI Corp., a specialty metals processor, was evacuated to check for structural damage after one car struck it.
"We have a small leak coming from one car. It's contained. There's a storm drain near it, but it's not into the storm drain," Stevens said. "The hazmat crews for the railroad are on site and will be taking care of that situation."
Norfolk Southern Railroad workers were examining each car to make sure there are no other leaks, the Valley News Dispatch reported. The derailment shut down the rail line.
Railroad officials had no word yet on the cause of the accident.
Stevens said the derailment occurred "within two hills where it's contained."
"If it had to happen, this is one of the better places for it to happen," he told WTAE.