An Australian drilling company has pleaded guilty to three health-and-safety violations in connection with a 2010 coal mine disaster in New Zealand that killed 29 miners.

VLI Drilling pleaded guilty Tuesday in a New Zealand court to charges that it failed to keep its workers safe at the Pike River coal mine. The company faces a maximum fine of 750,000 New Zealand dollars ($607,000 US). VLI, a contractor at the mine, employed three of the men who died. Several criminal charges also are pending against the main mine operator, Pike River Coal Ltd., which employed the rest of the victims.

Bernie Monk, father of a Pike River Coal Ltd. employee killed in the disaster and a spokesman for all of the victims' families, said that VLI has been able to walk away without facing any meaningful consequences.

"For me it's only a slap on the wrist," Monk said. "It's very hard to defend."

Methane-fueled explosions

The men died after a series of methane-fueled explosions. The Labour Department said in a statement of facts about the case that it's not known if VLI's drill rig was running at the time of the first explosion. However, the department says VLI's methane detector on the rig was faulty and needed replacing, and hadn't been inspected as required.

Brett Lynch, the chief executive of parent company Valley Longwall International, emphasized in a statement that the charges didn't relate to the explosion itself. He said he regretted VLI not having in place proper procedures to ensure inspections were carried out.

"We regard the safety and wellbeing of our people as an absolute priority," Lynch said.

He said the company had provided "ongoing financial and practical support," to the families of the three dead miners, adding it would be inappropriate to disclose details.

'We've had to fight every inch of the way to be heard'—Bernie Monk, father of a Pike River Coal Ltd. employee killed in the disaster

Meanwhile, Pike River Coal Ltd. elected Tuesday not to contest nine health and safety charges. A court date is scheduled in October to determine the bankrupt company's culpability. Pike River's former chief executive Peter Whittall also faces 12 criminal charges, which he's vowed to fight.

At a government inquiry into the disaster, experts testified that the mine didn't have adequate escape routes or ventilation, and that Pike River Coal was cutting corners due to financial pressure. The inquiry is scheduled to issue its findings in September.

But Monk, whose 23-year-old son Michael died in the accident, said the failure to date by New Zealand authorities to hold anybody accountable in a meaningful way or to implement better safety procedures has him deeply frustrated. He said he and other victims' relatives will continue to push for both legal and mine safety reforms.

"We've had to fight every inch of the way to be heard," he said.

Monk said the families would consider civil litigation once the government inquiry concluded.

Lynch said he didn't expect civil litigation to be brought against his company because the safety charges didn't relate to the explosion.

The Labour department said in an email that any fines collected from VLI would go to the government rather than to the victims' families.