LEBANON — Maine State Police are still trying to locate a full-sized school bus that allegedly rear-ended a car Monday afternoon on the Carl Broggi Highway in Lebanon.

Two sisters, former residents of Lebanon who live in Massachusetts and were visiting the York County town Monday, told police that a yellow bus came up behind them and slammed into the back of their Buick Century, forcing the car into a ditch.

The women complained of neck and back pain but they were not transported to a hospital. Their identities have not been released.

None of the buses from School Administrative District 60, which serves the towns of Lebanon, North Berwick and Berwick, were in the area of the crash when it happened, officials said.

“It is kind of a mystery at the moment,” State Police Lt. Louis Nyitray said this morning. “It is going to be difficult until we get some information or see something out on the road to work with.”

Nyitray urged residents to call the State Police if they have seen a bus with front-end damage, or if they have other information that might lead investigators to the vehicle. He said it is possible that the bus is retired and is being operated by someone who has not changed the color from yellow, as required by state law when a school bus is converted for private use.

“The lucky thing is that no one was seriously injured,” Nyitray said.

Anyone with information concerning the crash should contact the Maine State Police at 657-3030.