Damage to a Greyhound bus is evident after it rolled over near Bezanson, Alta., east of Grande Prairie on Tuesday.

Alberta's Highway 43 had been sanded shortly before a Greyhound bus slid off the road and rolled early Tuesday, killing three passengers, Transportation Minister Luc Ouellette said Wednesday.

The bus, carrying 28 passengers and pulling a trailer of cargo,crashed on an icy stretch of highway about 50 kilometres east of Grande Prairie.

After the road was sanded, a pickup truck hit the ditch just before the bus came along and also slid off the road, Ouellette said.

"They actually had just sanded that right shortly before that truck got there, but I don't think that the sand and salt and calcium mixture they had put on had time to reallywork before the bus got there," Ouellette said.

The department will investigate the accident to determine ifmore could have been done to prevent it, he said.

A 20-year-old woman, Christa-Marie Olsen-Ramsey, and her five-month-old son, Taylor, were killed in the bus crash. They were from the Alberta village ofArdrossan, about 20 kilometres east of Edmonton.

A72-year-old woman, whose name has not been released, also died in the accident.

Vanessa Arsenault told CBC News how her 19-year-old brother, Nicholas, managed to escape with minor injuries.

"The window smashed when the bus flipped over and he fellout,"shesaid."There was three people nearly under the wheel of the bus, and they were all bleeding and everything, and there was, like, a baby under the bus."

Greyhound spokesman Dave Hickie saidthe driver had been with Greyhound for a year, but he could not say how much previous driving experience he had.

Other serious bus collisions in Alberta in recent years includea May 2005 collision of a semi-trailerand a chartered bus full of oilfield workers that had become stuck trying to turn around on a two-lane highway outside Edmonton.Six people died.

In August 2005, two people were seriously injured when a Greyhound bus collided with two large trucks in heavy fog east of Grande Prairie.