Four miners have died in an illegal rat-hole coal mine in Nagaland’s Longleng district, the Hindustan Times reported on Sunday, quoting officials. The open-cast mine is located in the Yonglok village on the Assam-Nagaland border and the miners who were killed have been identified to be Assamese. The police were informed about the deaths late on Saturday night.

Some locals alleged that the miners could have inhaled toxic gas but officials denied this. “Toxic gas did not cause the deaths, as some reports suggest,” Deputy Commissioner (Longleng) John Tsulie Sangtam told The Hindu. “Mining in the area had been suspended a month ago. The four had returned to collect their belongings but were caught in a mudslide.” The police official said a mudslide could have happened as it has been raining over the last few days.

In January, the Nagaland Cabinet had banned illegal coal mining in the state and imposed a provision mining ban on all firms and companies that had been issued mining licenses. The decision came after 15 miners were trapped in an illegal rat hole mine in Meghalaya’s East Jaintia Hills in December. Only five bodies have been discovered so far.

Sangtam said the deceased miners used to work at the illegal coal mine when it was still functional. He added that he is waiting for a detailed report on the incident.

Sangtam said a postmortem examination could not be conducted as the families insisted to take away the bodies, The Shillong Times reported. “The bodies were delivered after obtaining certificates from the families,” he said.