Fire crews northwest of Edmonton were busy Tuesday afternoon, after a fire broke out at a CN Rail trestle bridge northwest of Mayerthorpe.

Fire officials said a total of four fire departments were on scene fighting the flames at the peak of the fire Tuesday, with 24 firefighters on the ground.

CN has turned the investigation over to the the RCMP who are treating the fire as an arson investigation. Officials said due to the fire, roads were closed at Greencourt Road and Highway 22, and Range Road 85 north of Greencourt Road.

The fire prompted an industrial fire emergency alert after 2:30 p.m. – the alert said the fire started at about 1:30 p.m. fire crews were on site, along with CN Rail officials.

In addition, the Kreek’s Krossing Trailer Court and Mayerthorpe Junior and Senior High School had both been evacuated.

Officials told CTV News students were taken to the elementary school across town.

The alert urged residents to close their doors, windows and vents – and to take necessary precautions.

At about 6 p.m. the alert was lifted.

More to come...