A 67-year-old Butler County man died of an apparent heart attack at a Pittsburgh hospital following a head-on crash Monday night on Route 19 in Jackson Township, authorities said.

A 40-year-old Allegheny County woman also was seriously injured in the collision around 7:40 p.m. She was flown by medical helicopter to a Pittsburgh hospital and admitted in critical condition.

The wreck closed the highway between Little Creek and Mercer roads for about four hours.

Police identified the drivers, who were alone in their vehicles, as Michael J. Slavin of Lancaster Township and Shana Weiss of Sewickley. The investigation is continuing, Jackson Township police said. Slavin's official cause of death is still pending.

Slavin was traveling north on Route 19 when police believe the 2017 Toyota Corolla he was driving crossed the double, center line and struck Weiss' southbound 2004 Ford Focus.

Harmony Fire District volunteer firefighters and other emergency crews had to extricate both drivers from their cars. Both were talking to crews after the initial rescue.

Slavin, who was headed home at the time of the crash, was taken by ambulance to Allegheny General Hospital.

Jackson Township Police Chief Terry Seilhamer said hospital officials notified his department around 11:15 p.m. that Slavin had died of a suspected heart attack while in surgery for his injuries in the wreck.

The Allegheny County Medical Examiner's Office is also investigating to determine a cause of death. Police said they did not know if there would be an autopsy.

Weiss was flown to UPMC Presbyterian hospital. Seilhamer said police were later advised that she was in critical condition.

State police accident reconstruction specialists were called to assist, and investigators are also awaiting toxicology results from blood drawn from both drivers as part of standard procedure.