Solid, which has indicated that it would like to acquire the nearby Pike River mine from its receivers, said it had made a significant investment in infrastructure at Spring Creek to ensure it operated safely as it announced the higher annual coal production figures, which were driven mainly by strong performance at its Stockton mine.

But safety incidents have continued to dog Spring Creek, with four since late April, including a frictional ignition event revealed by Solid Energy chief executive officer Don Elder during the Pike River Royal Commission hearings.

Solid previously announced there was a small fire on a load haul dump as it drove out of the mine on the evening of April 29.

The other incidents included a high voltage cable flash from a shuttle car underground on May 6, and a similar flash incident from a continuous miner on June 19.

But the most serious incident Hampton raised was the frictional ignition incident on June 29.

Elder said the flame underground was described to be 6 feet high and 4ft wide and was caused by a McConnell Dowell operator who had been cutting stone.

A major investigation was underway of that incident but the “vehicle” (probably a continuous miner) involved was deemed to be compliant from the company’s preliminary findings, he said.

“But the water sprays may not have been adequately functioning at the time, which may well have been because they were clogged, I don't know, and that’s what our investigation is intended to find out,” Elder said.