The number of artisanal miners killed by a landslide at a copper and cobalt mine run by Glencore in southeast Congo rose to 43 on Friday and could climb further as the search for missing workers continues, local officials said.

Thursday's accident occurred in the KOV open-pit mine at the Kamoto Copper Company (KCC) concession near Democratic Republic of Congo's southern border with Zambia, in which Glencore subsidiary Katanga Mining has a 75% stake.

The original death toll was estimated at 36 but rose through Thursday evening and into Friday as more bodies were uncovered, the officials said.

"We think that other bodies are still under the rubble," said Joseph Yav Katshung, the director of cabinet for the governor of the Lualaba province where the incident occurred.

Officials said the miners were working on the site illegally and had no approval or permits, a common occurrence in south Congo and Africa generally. Old-fashioned and unregulated methods, which can compromise safety, cost dozens of lives a year in Congo alone.

A union official representing KCC employees, said a crack in part of the pit had been noticed on Wednesday. He said KCC had put up red warning signs, but the diggers had ignored them.

Glencore in a statement on Thursday confirmed 19 fatalities and said it was assisting search and rescue operations by local authorities.