Calgary police say three people were declared dead at the scene and at least 10 people were taken to hospital after a serious bus fire in the city's northeast Saddle Ridge neighbourhood on Thursday afternoon.

Officers responded at about 1:11 p.m. to the 800 block of Saddletowne Circle N.E. Police said one person sustained life-altering injuries, another sustained serious injuries, and a Calgary Police Service member sustained minor injuries and was taken to hospital. Officials later put the total injured at 16.

Calgary Fire Chief Steve Dongworth said 12 fire units responded, along with a hazardous materials unit, because the bus that caught fire ran on compressed natural gas. Police Staff Sgt. Andy Woodward said the collision involved two city buses and multiple other vehicles.

The cause of the collision and fire remains under investigation, and police closed access to Saddletowne Circle for an extended period. Premier Danielle Smith and Calgary Mayor Jeromy Farkas both expressed condolences on social media.