The miner who died in a rock collapse at the Ballarat Gold Mine this month was a contractor brought in to perform a controversial mining technique that the mine’s staff did not have the skills to carry out.

WorkSafe Victoria is investigating the incident that claimed the life of 37-year-old East Gippsland miner Kurt Hourigan and left 21-year-old Ballarat man Connor Smith with life-threatening injuries. Smith, who remains at The Alfred hospital in a serious but stable condition, was also a contractor.

The pair were engaged in a drilling technique known as air legging when the tragedy occurred 500 metres below ground on March 13. Air legging is a handheld form of mining that involves drilling into ground and rock using compressed air and water.

While it is not confirmed that air legging caused the collapse, the Australian Workers’ Union, which represents workers at the mine, has slammed the use of air legging. Ballarat Gold Mine has suspended the technique while an investigation continues.

The company that owns the mine, Victory Minerals, said the two men were employed by a separate company specialising in personnel and equipment for air legging because the mine’s own employees did not know how to carry out the technique.

“Both Kurt Hourigan and Connor Smith were employees of a contractor and engaged to undertake air-leg mining,” a Victory Minerals spokeswoman said.

Earlier this month, the Australian Workers’ Union said the two miners were working beneath unsupported ground when it collapsed.

The mine’s former health, safety and risk manager, Rick Walker, savaged the mine’s owners last week, saying Hourigan’s death was an “accident waiting to happen” and the company had been warned against air legging.