State police say it will take time to know why a tractor-trailer slammed into the path of a charter bus headed to Niagara Falls, killing the bus driver and two passengers.
Trooper David Peters said Thursday that a second tractor-trailer was involved, but they were still investigating what led to the accident.
Trucking company Cardinal Logistics Management Corp. said it was cooperating fully with authorities and "committed to learning the facts."
The crash occurred Wednesday morning on Interstate 380 in the Pocono Mountains region. The bus had departed from New York when police said say it collided with a tractor-trailer that had crossed into oncoming traffic.
More than a dozen people were injured and taken to hospitals. Two people remained in critical condition Thursday.
Eight people treated for mild to moderate injuries after a bus carrying Italian tourists crashed into a tractor-trailer in eastern Pennsylvania have been released from the hospital.
Geoffrey Roche, a spokesman for Pocono Health System, says the patients had all been released by Wednesday night.
State police are still investigating the crash which occurred when the truck headed south on Interstate 380 in the Pocono Mountains crossed into the northbound lanes, hitting another truck before the bus then hit the first truck.
The bus driver and two other passengers were killed. Seven other passengers remain hospitalized, four in critical condition.