Water levels in the 300-feet deep flooded coal mine in Assam’s Dima Hasao district receded by nearly 23 feet on Friday, boosting rescue efforts to locate eight workers trapped inside, The Hindu reported.

Not much progress had been made in locating the workers, who have been trapped inside the illegal rat-hole mine in the industrial town of Umrangso since Monday, despite efforts to drain the water using heavy pumps and scan the vertical shaft using sonar equipment.

However, the process of dewatering, or draining three abandoned mines within 500 metres of the flooded one, helped lower the water levels inside, District Magistrate Simanta Kumar Das said on Friday.

The three abandoned mines may be interconnected with the flooded mine by passages of narrow tunnels, according to The Hindu. The three mines were said to have been abandoned before rat-hole mining was banned in 2014.

“We noticed a significant improvement after five pumps were used on Friday to dewater the mines,” The Hindu quoted Das as saying. “The water level of the mine where the miners are trapped went down by about seven metres.”

The dewatering process was expected to speed up once the heavy pressure pump brought in from Maharashtra by Coal India Limited on Thursday began operating, the district magistrate added.

“It is a complex process,” Das said. “But we hope to press this pump into operation by Saturday evening.”

At least nine workers were trapped in the mine on Monday after sudden flooding left them no time to escape. About 15 labourers were present in the mine when an underground water source was accidentally breached, flooding the shaft and tunnels.

On Wednesday, the body of one of the nine missing workers was recovered by Army divers 85 feet below the surface. The person was identified as Ganga Bahadur Srestho from Udayapur district of Nepal.

On Saturday morning, the bodies of two more workers were retrieved from the mine, Chief Minister Himanta Biswa Sarma. One of them was identified as 27-year-old Lijen Magar, a resident of Umrangso, he said. The other body was yet to be identified.

Six workers are believed to be still trapped inside.

Officials from the Indian Army, Navy, the National Disaster Response Force, the State Disaster Response Force, the Oil and Natural Gas Corporation, Coal India and the district administration are collaborating on the rescue.

National Disaster Response Force official Kuldeep Sharma said that the workers were in the rat-holes connected to the central pit of the mine when it got flooded.

Rat-hole mining has been banned since 2014. It is considered to be an unscientific and dangerous technique in which workers enter deep tunnels around three or four feet high to extract coal. However, numerous instances of the practice have since been recorded across the North East, including in Assam.

Alleged mine financier detained

On Friday, the Assam Police detained an alleged financier of the mining operation from the 3 Kilo area in the district, The Hindu reported.

Hannan Laskar, who allegedly invested in the mining operation and kept workers under pressure to extract large quantities of coal, was detained in connection with the incident, the newspaper reported.

“We are questioning him to find out more about the illegal operations in the area,” an unidentified police officer told The Hindu.

On Tuesday, Sarma said that Punish Nunisa, who is allegedly the leaseholder of the mine, had been arrested in the matter.