Calgary police are looking for witnesses to an early morning crash that left a woman critically injured.

A 1999 Infiniti G20 left Stoney Trail at around 2 a.m. on Wednesday as it was exiting onto Harvest Hills Blvd. N.W., police said. 

The vehicle struck a tree, causing it to roll over. The car ended up on its roof in the northbound lane of Harvest Hills Blvd. 

The 20-year-old woman driving the car was ejected — leaving her with critical head and neck injuries, police said.

She was the lone occupant of the car and was not wearing a seatbelt. 

Alcohol, speed and driver error are being investigated, police said. 

Anyone who saw the crash is asked to call police or Crime Stoppers