Chatham-Kent OPP said on Saturday they are continuing to investigate a serious head-on collision between a van and ambulance that left a man in critical condition.

Chatham-Kent EMS and police were called to the crash near Green Valley Line and Highway 40 around 10:30 a.m. Friday.

OPP are asking anyone with information to get in touch with them.

The male minivan driver, Geoffrey Brereton, 60, of Chatham, was airlifted to a London hospital.

"It appears based on the very early evidence at the scene that the minivan crossed the centre line into the path of the ambulance and it was more or less a head on collision," says Sgt. Brian Knowler.

Police say the ford minivan was headed north on 40, and the ambulance was heading south.

The ambulance was not on call and was not carrying a patient, say police. The driver of the ambulance suffered minor injuries.

Police say another paramedic inside the ambulance, escaped without a scratch.

OPP technical traffic collision investigators are looking into the cause of the crash.

Anyone with information, which may assist in the investigation, is asked to contact Provincial Constable T. Braun of the Chatham-Kent OPP Detachment at (519) 352-1122.