JOHANNESBURG – Sibanye Gold says workers failing to follow rules and procedures are largely to blame for a spike in fatal accidents at its South African operations, where 19 people have died since January.

The company accounts for more than a third of the deaths in South African mines this year and faces growing criticism from unions and government. In the latest incident, four workers died and one was still missing on Tuesday at its Kloof operation.

“It is inexplicable to us,” Sibanye spokesperson James Wellsted said of the increase in fatal accidents. “We think a lot of it is behavioral and due to people taking risks and not following safety procedures.”

Sibanye, which is the biggest gold mining employer in the country and operates some of the deeper mines, is asking unions and government for help to get workers to comply with procedures and arranged a ‘safety summit’ last month to discuss the issues.

The company employs 64,502 people including contractors in South Africa, where mining safety has been a problem for decades. The country’s mines are among the world’s deepest and oldest, with workers going as deep as 3 km (1.9 miles) in search of ore that’s been mined commercially for over a century.

While safety has improved since the end of apartheid, fatalities in the sector increased last year for the first time in a decade.

The workers who died at Kloof this week had strayed into an abandoned area with no ventilation, Wellsted said. It’s unclear what they were doing there, he said.

The area should have been barricaded, said National Union of Mineworkers Secretary General David Sipunzi. Sibanye “must take responsibility” for the deaths and should be forced to shut down all its mines to allow for a full safety inspection, the union’s safety chairperson, Peter Bailey, said separately.

Sibanye fell 4.7% by 2:43 p.m. in Johannesburg, extending this year’s drop to 42%.

Last month, seven people died at Sibanye’s Driefontein mine after an earth tremor triggered a rock-fall. In February, nearly 1 000 workers were trapped underground for more than a day at Sibanye’s Beatrix mine after a severe storm damaged electricity lines cutting off power supply.

Earth tremors, or seismic events as the companies call them, are regular occurrences in deep mines, said Bernard Swanepoel, a former CEO of Harmony Gold and board member of Impala Platinum. When orebodies become narrower as reserves run out, it becomes more difficult to automate the operations to keep workers away from dangerous areas.

“To pretend there is no risk is misleading,” Swanepoel said. “Unfortunately deep-level mining is inherently a lot riskier.”

There’s not much companies can do to completely eliminate mining deaths, said Rene Hochreiter, analyst at Noah Capital Markets.

“The alternative is to shut down gold mines completely,” he said. “The fatalities are negative for Sibanye, but at the risk of sounding flippant, that’s life. You never get zero fatalities at deep-level mining.”