Dima Hasao District Magistrate Simanta Kumar Das said that the process of ‘dewatering’ or draining three abandoned mines within 500 metres of the ill-fated mine helped lower the water level within it. It is possible that these mines – each with a network of narrow tunnels branching out from the wall of a vertical pit – could be interconnected.

The four deceased labourers are among the nine workers trapped inside the coal mine in Umrangsu on Monday after a sudden gush of water flooded the quarry.

The death toll has climbed to four after three bodies have been recovered today; five workers still remain trapped.