Death toll reached 61 on Tuesday, resulting from an underground fire that killed illegal miners at the disused Eland gold mine in South Africa, Harmony Gold Mining Co. said.
"Today we found 25 more bodies," said Tom Smith, head of Harmony's operations in South Africa's central province Free State, on Tuesday. "The bodies are not burnt. It seems more of a case of gas or smoke inhalation."
Illegal mining in South Africa's abandoned gold mines often goes unnoticed because miners can sneak past security at one mine and exit from another owned by a different company kilometers away. The illegal miners can stay underground for months unseen.
Recent record-high gold prices have made the risk taken by well-organised illegal mining syndicates even more worthwhile.
Harmony, the world's fifth largest gold producer, is particularly exposed to plundering by illegal miners compared with its peers, because it was pursues a strategy of buying old, unwanted gold shafts and mines.
Smith said the bodies were retrieved by fellow illegal miners from depths of up to 1.4 km (0.9 miles).
He said he didn't know how the fire had started, and reiterated that it was too dangerous for Harmony to send its staff to search for bodies.
"I don't know if there are any more bodies down there, we just have to wait," he said.
The illegal miners were killed in a fire over the weekend at Harmony's Eland shaft, located in the Free State. A similar fire in 2007 at its marginal St. Helena mine in the same province killed 23 illegal miners.
The Department of Mining, which is grappling with an escalating safety crisis in South Africa's mining sector, said that dealing with illegal miners was difficult because it lacked enough staff to inspect operational mines, let alone disused ones. Illegal miners are also usually armed.
South Africa's Chamber of Mines, which groups gold producers in the world's third biggest source of gold, said illegal mining was a problem that individual companies were dealing with, but it had no figures on the value of gold stolen.
Police have conducted sporadic sting operations to arrest the illegal miners, but mine owners say catching thieves was difficult in the labyrinth of mines.
Minister of Mining Susan Shabangu expressed condolences for the deaths at the Harmony mine, and promised to visit the site of the deaths on Tuesday.
(Editing by Matthew Tostevin)