A semi driver accused in the deaths of three teens from Carrot River, Sask., has pleaded guilty.

Norman Lavoie entered pleas to three counts of dangerous driving causing death and one count of dangerous driving causing bodily harm Tuesday in a Melfort court.

The charges stemmed from a fatal crash May 3, 2015, on Highway 6, near Spalding in central Saskatchewan.

A car was stopped in a construction zone when it was rear-ended by a semi-tractor trailer, according to RCMP.

The car was pushed forward into a pickup truck, which then struck a highway flag person before colliding with a construction pilot vehicle.

The three people in the car — 17-year-old Carter Stevenson, 15-year-old Kristian Skalicky and 14-year-old Justin Gaja — were pronounced dead at the scene.

The flag person, a 21-year-old B.C. man, was flown to hospital in Saskatoon with critical injuries.

Lavoie, from Winnipeg, was taken to hospital in Melfort alongside the drivers of the pickup and pilot vehicle. All three sustained minor injuries, police said.

Lavoie was initially charged with criminal negligence causing death and criminal negligence causing bodily harm, but pleaded guilty to the lesser charges Tuesday.