York Regional Police say they have been called to a location on Applewood Crescent, in the Highway 400 and Highway 7 area.
Police say two workers are involved and one has died.
The coroner is attending the scene.
Ornge air ambulance says that it is transporting a man in his 50s to a Toronto hospital.
The patient was crushed under a door. He was having trouble breathing and had suffered back and head injuries, Ornge said.
Both Ornge and paramedics reported three individuals being involved in the incident. The reason for the discrepancy in the number of people quoted by police was not immediately clear.