INDORE: At least six were killed and another critically injured after an out-of-control trailer travelling on the wrong side of the road collided head-on with their car on the Badnawar-Ujjain four-lane road near Panchkawasa village in Dhar district on Sunday afternoon.The accident occurred around 1pm when the victims were returning to Gujarat after visiting the Mahakaleshwar temple in Ujjain.According to preliminary information, the trailer was travelling on the wrong side of the road when it rammed into the car. The impact was so severe that the car was completely mangled, killing six occupants on the spot.The seventh occupant sustained serious injuries and was pulled out of the wreckage with the help of local residents. He was taken by ambulance to the Civil Hospital in Badnawar, where he is undergoing treatment.All six deceased were residents of Vadodara in Gujarat. Police have informed their families about the accident.Badnawar police station in-charge Amit Singh Kushwah and Tehsildar Suresh Nagar reached the spot along with police personnel soon after being alerted.The bodies were extricated from the mangled car and sent to the Badnawar Civil Hospital mortuary. Police said the bodies would be handed over to the families after postmortem examinations and completion of the necessary formalities.Traffic on the four-lane road was affected for some time following the crash but was later restored.Police have launched a further investigation into the circumstances leading to the collision.