LUSAKA, Zambia (AP) — Eleven informal miners have been confirmed dead and their bodies retrieved from an open-pit copper mine in Zambia after landslides buried them in tunnels they were digging last month. One survivor has been found but up to 26 others remain missing and are feared dead nearly two weeks after the disaster.

Rescuers announced the latest death toll late on Sunday. The survivor, a 49-year-old man, was pulled out from underneath the debris last week and is recovering in the hospital, said the Disaster Management and Mitigation Unit, which is overseeing the rescue operation.

Rescuers also retrieved the first two bodies last week. Nine more were recovered this weekend, the disaster management unit said.

Government officials say as many as 38 miners might have been buried under the landslides at the mine near the city of Chingola, on Zambia’s copper belt, although they aren’t certain of the exact number.

They have been relying on families to report missing relatives and fears were growing that the death toll could rise to more than 30.

“Efforts to recover the remaining accident victims are ongoing,” the Disaster Management and Mitigation Unit said in a statement.

The disaster happened Nov. 30 when heavy rain caused landslides and the miners were buried in three separate tunnels while working in them late at night. The rain also caused the area around the tunnels to be flooded and rescuers have had to pump out water from the site as well as clear rocks and earth. The army has been helping with the rescue operation.

The miners are believed to have been digging for copper ore illegally without the knowledge of the mine owner, making it difficult for authorities to know exactly how many were trapped underground.

Zambia is among the top 10 copper producers in the world. Chingola, which is around 400 kilometres (250 miles) north of the capital, Lusaka, has large open-pit mines, some of them stretching for kilometres (miles). They are surrounded by huge waste piles of rocks and earth that have been dug out of the mines.

The government said debris from one of the waste piles is thought to have collapsed on the miners’ tunnels in the heavy rain. Informal mining is common in the area, where small-scale miners go underground without proper safety precautions.

Police said in the days after the tragedy that they believed that most of the miners were dead, but were criticised by the government, which said it was too early to make that statement.

Zambian President Hakainde Hichilema visited the mine last week and said he retained hope that there might be more survivors.