A former New Zealand coal mine boss pleaded not guilty Thursday to 12 labor law violations involving the underground explosion nearly two years ago that killed 29 miners.

Former Pike River Coal chief executive Peter Whittall is charged with knowing about or participating in the failures of the company and with failing to ensure that none of his actions harmed any of his employees.

The victims' bodies are still entombed in the Pike River mine because the methane gas buildup that caused the explosion has made a recovery operation too risky.

At the government's ongoing investigation, experts have testified the mine didn't have adequate escape routes or ventilation to rid it of explosive gasses and that the financially strained coal company was cutting corners.

Whittall's charges relate to his alleged failure to manage the mine's ventilation and mitigate the risk of explosions. Whittall's lawyers say their client is a longtime coal miner who would never do anything to put his workers at risk and that he is being made a scapegoat.

His next court appearance is scheduled for March. Each of the charges against him carries a maximum penalty of 250,000 New Zealand dollars ($204,000).

New Zealand police are still considering whether to lay more serious charges against Whittall.

Meanwhile, Australian company VLI Drilling, which was contracted to perform work at the mine, is due to be sentenced Friday after pleading guilty to three labor violations.

And the now-bankrupt Pike River Coal company has pleaded not guilty to nine labor violations, although the company has told a judge it will not offer any defense against the charges. That means a judge will consider evidence against the company submitted by government lawyers and decide upon a verdict.