LANCASTER, Pa. — Police say a 27-year-old mother has died and her two children have been hospitalized following a head-on collision with a tractor-trailer in Pennsylvania.

Police say the crash happened around 9 a.m. on state Route 72 in Lancaster County. The woman’s 3-year-old is in critical condition, but her 18-month-old is expected to be released from the hospital.

The woman’s identity has not been released, pending family notification.

Officials say the 47-year-old truck driver, of Lancaster, has been hospitalized with injuries that are not life-threatening.

Police say their preliminary investigation shows the truck was traveling south and the sedan was traveling north when the woman’s car crossed the center line.

An investigation is ongoing.