A York Region paramedic is in hospital with serious injuries after the ambulance he was riding in collided with a transport truck.

The accident occurred at 16th Avenue near Leslie Street, in Richmond Hill, at about 10 a.m.

Police said the tractor-trailer plowed into the driver's side of the ambulance, which had its sirens and lights activated.

The injured paramedic was treating a patient in the back of the ambulance and was tossed around on impact.

The paramedic was taken to hospital with serious but non-life-threatening injuries, police said.

The paramedic at the wheel of the ambulance also suffered less serious injuries, while the patient was not hurt, police said.

The accident closed 16th Avenue to traffic in both directions. The cause of the crash is still under investigation.