At least two persons were killed and one missing after a coal mine collapsed in Mooknor on Sunday. S Nongtnger, superintendent of police, East Jaintia Hills, said: "It is suspected that boulders hit them while they were trying to extract coal. The investigation is underway to identify the owner of the quarry." East Jaintia Hills is same the area where at least 15 miners are trapped in an illegal coal mine since December 13. Its owner has been arrested.