Tower colliery in south Wales is back in full production three months after an earthquake caused a massive leak of potentially explosive methane gas.

It has cost £500,000 to tackle the problem which has had a serious effect on the pit's financial position.

The tremor presented the biggest challenge yet to the pit at Hirwaun in the Cynon Valley - rescued by a workers buy-out when the colliery was threatened with closure in the early 1990s.

The V40 face had been open just a few weeks when the earthquake struck.

Initially, workers reported only minor damage underground but later more serious problems developed and cracks caused by the tremor led to a flood of methane gas.

A total of £500,000 has now had to be spend laying a three-mile pipe underground and drilling 15 bore holes to drain away the gas.

The pit lost nine weeks of production which has had a serious effect on sales and profits.

But this week they are back in full production and in confident mood.

"It was very worrying for all of us. It's a major problem to not be able to coal for a period of that time," said managing director Geoffrey Davies.

"So to be back in production is something we're all very pleased about."

On the first day back in production, almost 2,000 tonnes was produced from the new face - a new record for the pit.

But the full cost of the problem will become clearer at the pit's annual meeting to be held in the spring.