STORY: Rescue efforts have been ongoing since the flood on April 16, but there has been no communication with the missing miners and it is not known whether any survived.

"Given the dry season obviously we do not expect rain and we had an absolute torrential downpour," said Hein Frey, Vice President of Operations at Trevali, adding that the water crossed one of their bridges and broke safety barriers.

Frey said the company called for help immediately and by the next day other mining companies in Burkina Faso had sent rescue teams and pumps. Water is still being pumped out of the mine.

While most workers underground were able to safely evacuate, the eight missing were below Level 520, which is 520 metres (1,706 feet) from the surface, at the time of the flooding, the company said.

There are two safety chambers stocked with food and water below that level, but it is not known if any of the men were able to reach them.

Trevali CEO Ricus Grimbeek said there was hope but added the safety chambers were not designed to be submerged in water.

The company and Burkina Faso's government have launched investigations into what caused the accident.