Rio Tinto to Restart Underground Operations at Oyu Tolgoi Copper Mine — 2nd Update

By Rhiannon Hoyle

Rio Tinto is preparing to restart underground operations at the Oyu Tolgoi copper mine in Mongolia after a seismic event triggered a rockfall that injured two employees.

The company had paused underground activities after seismic activity occurred along a rock fault zone at roughly 6:00 p.m. local time Thursday, resulting in ground vibration in the mine.

"Following a systematic and staged assessment, we are now preparing to commence a safe and controlled restart of operations," said Oyu Tolgoi LLC, in which Rio Tinto owns a 66% stake. The Mongolian government owns 34%.

"A preliminary inspection has identified that the localized rockfall is confined, with no structural impact to the cave or its operating infrastructure," it said in a statement Friday.

Two employees are receiving treatment in Ulaanbaatar for non-life-threatening injuries, it said, adding that 13 other employees were discharged locally after being assessed.

Rio Tinto has been ramping up underground mining at Oyu Tolgoi, where open-pit operations began in 2011 but the most valuable copper resources lie deep beneath the Earth's surface.

Earlier this month, the miner reported a 29% increase in Oyu Tolgoi copper production year to date. It expects that, by 2030, Oyu Tolgoi will be the fourth-largest copper mine in the world.

Write to Rhiannon Hoyle at rhiannon.hoyle@wsj.com

(END) Dow Jones Newswires

October 30, 2026 03:58 ET (07:58 GMT)