BARRIE -- The Special Investigations Unit is appealing for witnesses to a collision involving a pedestrian and an unmarked police vehicle overnight on Tuesday in Midland.

The SIU says an OPP officer was travelling east on Highway 12 near Jones Road when her unmarked SUV struck a man as he crossed the road shortly after midnight.

The officer attempted first aid on the man until paramedics could take over.

The 35-year-old Pembroke man died at the scene.

"It's a very sad situation," said OPP Const. Aaron Coulter. "Officers spend many hours throughout the year, and nobody wants to see someone hurt on the road."

The intersection was closed for nearly 14 hours for the investigation.

Four investigators, two forensic investigators and one collision reconstructionist are working on the case to determine whether road and weather conditions were a factor in the deadly incident.

The SIU is an independent civilian agency that investigates reports involving police where there has been death, serious injury or allegations of sexual assault.