The mine has two chambers – and they are a place of safety and contain essential supplies like water and food.
“The rescue teams have opened the refuge chamber [estimated to be at a depth of about 570m], unfortunately it is empty,” Reuters quotes the government’s information service as saying.
The mine, which is owned by Canadian firm Trevali, has a depth of more than 710m (2,329ft) – and a second rescue chamber is located at the bottom.
A search is ongoing, according to the same information service, and will continue until any person is found alive or dead.
The mine is located about 100km (60 miles) west of the capital, Ouagadougou.
Last week, the Canadian mine owners said search crews were working 24 hours a day to find the workers.
The case has caused outrage in Burkina Faso, as rescue operations only got under way following protests and a sit-in at a government building at a nearby town five days after the floods.
The area saw heavy thunderstorms on 16 April that cut off electricity and communications.
