MOUNT GRETNA, Pa. — A Greyhound bus bound for St. Louis from New York City flipped on its side on the Pennsylvania Turnpike early today, briefly trapping a woman and injuring about two dozen people, authorities said.

Twenty to 25 injuries were reported, turnpike spokesman Carl DeFebo said, and rescue crews freed the woman who was trapped in the wreckage in a rural area about a mile east of the Lebanon-Lancaster exit.

The westbound bus had stopped in Philadelphia and was to stop again in Pittsburgh when it overturned about 6 a.m., DeFebo said.

Both westbound lanes of the turnpike were closed, forcing drivers off the interstate at the Reading exit to be rerouted to the Harrisburg East exit. Traffic was backed up for about three miles by the time vehicles were allowed to pass through on the shoulder of the highway around 8:30 a.m., while crews worked to upright the bus, DeFebo said.