GAS blows in an area of a mine where a worker was killed last year were getting larger and more frequent in the run-up to miner John Anderson’s death, an inquest was told.

Mr Anderson – known as Richie – was killed in what is believed to be the biggest gas blast in a generation almost a mile underground at Boulby Potash Mine in east Cleveland, in June last year.

The 56-year-old miner, who had decades’ worth of experience, was operating a remote-controlled mining machine when it drilled into a pocket of methane, causing the walls of the mine to blow out.

Mr Anderson, from Easington village, near Boulby, was buried underneath a mound of rubble – but rescue teams were unable to dig him out until two hours later due to lethal levels of gas still being present, and the risk of further blowouts.

Teesside Coroner Claire Bailey said evidence had been heard from one worker that there had been gas blows in that part of the mine every shift since February last year.

She said: “Over the last few weeks they were getting bigger and more frequent. There was a considerable amount of rubble with the most recent one before the accident.”

She asked shift manager John Welsh: “When would it get to the point where the mine says, we are not going to mine in that district anymore?”

Mr Welsh said it was considered safe, with the extra precautions that are undertaken in high-risk areas of the mine.

He described how he arrived at the scene of the blowout and prevented the man from looking for Richie because of the high gas levels.

He said: “There was a very large debris field, about 2.5m deep. I moved a few rocks and some of the pieces of rock were quite large.”

His voice cracked as he said: “I thought that Richie was almost certainly dead underneath.”

Electrician John Marley, who was on the same shift as Mr Anderson, described how a curtain between the bait room and mine road lifted and blew across the table at the time of the accident.

He said: “When this happens you know there has been a gas blow. It lifted twice, it lifted up above head height, and I felt a whoosh of hot air.

“It seemed bigger than any I had seen before, due to the way the curtain lifted.

“Three lads came back and said Richie was missing. We walked up to where the gas blow was. I could see the miner (machine) to the left and there was a mountain of muck and rubble from the floor to the roof.

“We were all shouting for Richie but there was no response. The gas detectors were flashing like mad. They were reading over five per cent which indicates dangerous explosive levels of methane.

“Everyone wanted to dig Richie out but we couldn’t stay there because of the gas."

The inquest, at Teesside Coroner’s Court, heard that two days before the accident there was a blowout with gas readings “off the scale”.

But Mr Welsh said: “At that time it was still considered safe.”

However, he said mining had stopped immediately in the area of the accident.

It had resumed in an adjacent area but there were further gas blows, and the area was abandoned.

James Robinson, acting for Mr Anderson’s family, said: “You keep going until something terrible happens, until you have to stop. Did you have anything in place saying no, we are not going to keep going until something fatal happens?”

The inquest continues.