Authorities say an accident in eastern Pennsylvania involving two tractor-trailers and a school bus from New Jersey sent five students and four adults to hospitals.

State police in Northampton County said said the bus was heading uphill in the westbound lanes of Interstate 78 in Lower Saucon Township shortly before 10:30 a.m. Tuesday when it "experienced unknown engine problems" and slowed down.

Police said a tractor-trailer trying to drive around the bus sideswiped it and then hit a tanker trailer. Five students, the bus driver and another adult were taken to Saint Luke's Anderson. Both truck drivers were taken to Saint Luke's Fountain Hill.

Wayne Township officials said the bus was carrying 37 Wayne Valley High students, a teacher and a counsellor on a senior class trip to Dorney Park.