At least 50 people died on Thursday after a landslide at a jade mine in northern Myanmar trapped workers under a mound of refuse, authorities said.

The miners were collecting stones in the jade-rich Hpakant area of Kachin state when a wave of mud caused by heavy rain buried them, the fire service department said in a Facebook post.

“Now in total 50 dead bodies,” the post said. “We are still working on the rescue process.”

Deadly landslides and other accidents are common in the poorly regulated mines of Hpakant.

Media have reported scores of people killed in Hpakant in recent years, many of them freelance “jade pickers” who scour tailings – the residue from mining – for stones that have been missed by larger operators.

Tar Lin Maung, an information ministry official in Hpakant, told Reuters by phone the landslide on Thursday happened in the early morning.

Official sales of jade in Myanmar were worth 671 million euros ($750.04 million) in 2016-17, according to data published by the government as part of an Extractive Industries Transparency Initiative.

But experts believe the true value of the industry, which mainly exports to China, is much larger.

Reuters