Rescue workers have recovered one of the bodies, found overnight, inside the small private Gleision Colliery in the Swansea Valley.

The families of the four men have all been informed about the latest discovery, but formal identification of the three bodies has yet to take place.

Three other men had escaped from the mine following the accident on Thursday and one was taken to hospital. Emergency services said a wall to an old working had failed, flooding the main 250-meter route into the mine.

Rescue workers found the body of one miner at the bottom of a shaft and the second at the place where they had been working at the time of the accident.

It is not known at this stage where the third body was found.

Rescue workers had to clear a way past a blockage caused when water had rushed in, before gaining access to the main shaft at the bottom of the mine.

Crews have now begun searching the “myriad” of tunnels and offshoots from the main shaft, but it is expected to be slow progress as they have to dig through silt and debris swept down by the flood.

Wales, once famous for the mines in its valleys, has only a handful of remaining working mines, small and privately held, mostly supplying thermal coal for power stations.

Gleision Colliery is a private mine operating under a steep hillside above the banks of the river Tawe.

The colliery is a drift mine, a relatively low-cost form of underground mining, when tunnels — drifts — are dug horizontally into rock, rather than directly downwards.

Drift mines were known for being very dangerous in the past, with frequent accidents as tunnels caved in, and they remain risky.