Three other miners managed to escape as the flood engulfed the drift mine.

BBC: Gleision mine deaths: Prayers for miners and families

The four men died after the Gleision drift mine flooded on 15 September 2011 after a retaining wall holding back a body of water failed.

BBC: Gleision mine deaths: Prayers for miners and families

It is a small drift mine - a mine cut into the side of a hill, where the coal seam is accessed by walking in.

BBC: Welsh mine rescue: Third Gleision miner found dead

Emergency services, including firefighters, an ambulance, and the air ambulance were called to the Unity pit, which is a drift mine like Gleision, at about 09:30 BST on Friday.

BBC: Miner rescued after pit collapse in Neath Valley

Two more men escaped unaided from the drift mine - a mine cut into the side of a hill where the coal seam is accessed horizontally - before emergency services arrived.

BBC: Trapped miners: Bid to rescue men in Swansea Valley