Four women were killed on Sunday when a closed coal mine in Madhya Pradesh’s Betul district caved in, IANS reported.

The accident took place when local women were illegally extracting coal from Satpuda 2 coal mine of Western Coalfields Limited, Betul Sub-divisional Magistrate SK Bhandari told the Hindustan Times. “The accident spot is actually the area where the coal was dumped,” said Bhandari. “The women were extracting coal illegally from the aggregate when it caved in.”

Betul Superintendent of Police DR Senwar said five women were trapped when the accident took place. Of them, four died and the lone injured woman has been admitted to a hospital.

A search operation is on to check if people are still trapped under the debris. The deceased were identified as residents of Kalimai area. Senwar added that an investigation was underway.

In 2016, two people died when the roof of a coal mine collapsed in Umaria district. In 2012, six people were killed when an illegal coal mine caved in at Bargawan area in Singrauli district.