STARS Air Ambulance was called about 20 kilometres north of Regina on Highway 6 on Tuesday morning.Emergency crews had the road blocked off in both directions after what RCMP called a serious crash at about 8 a.m. that injured at least one person.Off the northbound side of the road, a small red SUV could be seen with damage to its front end.A heavy truck was also stopped on the northbound shoulder. Police say it was a semi-truck hauling gravel.The public is being asked to avoid the area.Police say the highway will be closed for about four hours until the investigation is complete.