LUSAKA, Zambia (AP) — More than 30 people are trapped under rubble at an open-pit mine in Zambia after part of a waste pile was thought to have collapsed on them, a government minister said on Friday.

Home Affairs and Internal Security Minister Jack Mwiimbu said in Parliament that the collapse happened in the city of Chingola, in Zambia’s copperbelt, about 400 kilometres (248 miles) north of the capital, Lusaka.

“May I just inform the nation that we have a tragedy that is brewing in Chingola, where a number of our people have been affected by a collapse of the open pit,” Mwiimbu said. “We have more than 30 people under the rubble and we are struggling to retrieve them.”

He said rescue teams were at the site.

Mines and Minerals Development Minister Paul Kabuswe was also at the scene and said no one had yet been found and it wasn’t clear exactly how many people were trapped under the rubble.

Informal artisanal mining is common in Chingola, although the ministers didn’t say if those trapped were informal miners.

The southern African nation is among the top 10 biggest copper producers in the world. Cobalt is also mined in Chingola.

Chingola is home to one of the biggest open-pit mines in the world, which is a series of workings that stretch for more than 10 kilometres (6.2 miles). The area is marked by huge waste dumps made up of rock and earth that has been dug out of the mines.