All 1 800 miners who were trapped underground at Sibanye Stillwater in Rustenburg in the North West have been brought to the surface, the Department of Mineral Resources said on Tuesday.

Efforts had been underway to hoist up those remaining after an accident had blocked a shaft used to transport miners, James Wellsted, Sibanye’s spokesman, said. The company had been trying to bring them to the surface since 2 p.m. local time.

Workers had congregated at pick-up points about 1.5 kilometers (0.9 miles) underground after an accident with their transport system, he said, adding no serious injuries had been reported.

The incident revives concerns about safety at Sibanye, which last year suffered a spike in fatal accidents at its gold mines.

About 1,000 workers were also trapped underground for more than a day at one of the producer’s operations in February 2018 after a storm damaged power supplies in the area.

South Africa, which is the world’s biggest platinum producer, has the deepest mines in the world.

Sibanye shares closed 2.8 percent lower at 13.45 rand in Johannesburg on Tuesday.