Police are investigating a collision between two large, gravel haulers on a service road in the southeast.

The crash happened at about 2:15 p.m. Thursday on a service road near Deerfoot Trail and Southland Drive SE.

Police say the crash happened when one of the trucks struck the pup trailer of the second truck as they passed on the road.

The driver of the first truck was trapped in the cab and firefighters had to use hydraulic rescue tools to free him.

"It appears at this time that the dump truck that was travelling southbound crossed the centre line and for unknown reasons struck the northbound dump truck, so that is being investigated at this time," said CPS Sgt. Jason McDonald.

The injured man was turned over to EMS at the scene and was originally in serious condition. His condition has since been upgraded to stable. The other driver suffered minor injuries.