Perth-based mining contractor Byrnecut, already under scrutiny for two employee fatalities in Australia, is now at the centre of an international investigation after eight workers died in a West African mine disaster. 

The ABC has confirmed eight men who were trapped underground at the Perkoa zinc mine in Burkina Faso last month, were all employed by Byrnecut.

The company was awarded "full development and production contract" for the mine by its Canadian owner, Trevali, in 2016. The scope of the work included development, all stope production activities, haulage, all fleet management, and workforce training.

On April 16, unseasonal torrential rain inundated the West African mining site and cut off contact with eight employees — six Burkinabes, one Tanzanian and a Zambian — who were working over half-a-kilometre below ground.

The downpour crossed one of the mine's bridges and burst through "safety barriers" before damaging electricity and communications systems.

A massive month-long rescue operation ended last week after crews discovered no survivors had reached a rescue chamber 570 metres underground, exhausting all hope the men might still be alive.

Byrnecut confirmed the eight deaths in an internal memo, obtained by the ABC, which also said the company was in "close communication" with the affected families. 

The families of six miners, according to an Al Jazeera report, have filed cases over their deaths, claiming attempted manslaughter, endangering life and failing to assist a person in danger, against "persons unknown".

Burkina Faso Prime Minister Albert Ouedraogo launched a judicial investigation into the tragedy and arranged for the passports of the mine managers to be confiscated while inquiries were ongoing.

During a visit to the site at the weekend, Mr Ouedraogo also blamed "irresponsibility" by those in charge at the mine and alleged that several days before the accident "dynamite was used on the open-air [part of the] mine, which weakened the [underground] gallery and enabled the flooding".

Byrnecut and Trevali, both of which will be the subject of the judicial investigation, declined to be interviewed and did not answer specific questions about their responsibilities for decisions made in the lead up to the tragedy.

Mine safety consultant Stuart Vaccaneo said there were questions as to why the water ever made it into the Perkoa mining site.

He said flooding was considered "critical" or "extreme" risks and companies should have accounted for factors such as the stability of the foundation, on-site use of water such as dams, as well as rain and flooding events.

"Water and mines just don't mix, you've got to keep water out, whether it be open cut or underground," he said.

He said investigators would be assessing the design of the safety barriers against the activities that took place at the mine in the days and months leading up to the tragedy alongside the mine's evacuation plan.

"When you design barriers, you've got to build in a safety factor, there's a lot of design work that goes into it depending on the base rock, how much water you're going to hold back," Mr Vaccaneo said.

"You've obviously got to have a stable base and if the underlying strata gets weakened, the whole thing is going to fall apart."

Trevali vice president of operations Hein Frey, who visited the site earlier this month, said the rain was "completely unexpected".

"Given the dry season obviously we do not expect rain and we had an absolute torrential downpour," he told Reuters.

Two Australian mining deaths under investigation

The Perkoa mine tragedy follows two fatal incidents at mines involving Byrnecut in Western Australia and South Australia, which are still being investigated by safety authorities.

Young father of two, Michael Johnson, was killed in July 2020 while working for the company on a mine north-east of Kalgoorlie, WA.

He died at Saracen Mineral Holding's Dervish underground gold mine after the loader he was driving fell 25 metres over the edge of an open void in the mine.

Byrnecut holds the four-year mining services contract worth $440 million.

An interim report by Western Australia's Department of Mines, Industry Regulation and Safety Investigations (DMIRS), investigating the deaths and involvement of all companies at the site, concluded there were no visual markings to indicate a drop from the edge of the stope where Mr Johnson fell.

DMIRS said it was also investigating another incident from April 2020, where a Byrnecut employee was injured after a rockfall at an underground mine.

It said it was unable to comment further on Mr Johnson's case as its investigation into the fatality was still underway and was yet to determine the cause of the death.

Last September, a 43-year-old South Australian man was crushed to death by machinery while working on Oz Minerals Prominent Hill site south-east of Coober Pedy, SA.

Byrnecut has, since 2010, the contract to "undertake all underground activities" at the site, including "development, longhole drilling and charging, paste fill, stope bogging and fibrecrete batching and application".

SafeWork SA said it was still investigating the Prominent Hill death.

"After an investigation is conducted, SafeWork SA may issue charges against a person or business for breaches pursuant to the Work, Health and Safety Act 2012," a spokesperson said.

Mr Vaccaneo said mine safety standards had fallen across Australia as identified in the Grosvenor Inquiry and the Black Lungs, White Lies report tabled in Queensland Parliament in 2017.

He said, without connecting the three fatal accidents involving Byrnecut, any company experiencing deaths across its operations suggested the need for review.

"If you're any organisation and you're having fatalities across different parts of your operation you've got some major things to look at," he said. 

"You owe a duty of care to your employees — if they're dying at different operations — two things are wrong: either systems operating under the company are not good enough or the systems the people operating under aren't good enough."

Byrnecut executive chairman Steve Coughlan confirmed the men were under his company's employ. He declined to answer specific questions about the deaths, telling the ABC the company's focus is on recovering the bodies of the men while pumping out the hundreds of millions of litres of floodwater out of the mine.

Over 55 million litres have been removed, equating to roughly a third of the total amount thought to have swept through the underground portion of the Perkoa mine during the downpour.

Mr Coughlan said the company was assisting government authorities in their investigations and had launched its own, which will be conducted in collaboration with mine owner, Trevali.

Africa has been a major investment hub for Australian miners in recent years.

The number of Australian firms operating in African mining and oil projects has almost tripled to 220 across close to 600 projects over the past 15 years, according to an Australian government survey.