Colombian rescuers have found four bodies in a collapsed gold mine as they kept up a search for rest of the 15 workers, according to the emergency teams dealing with the issue.

Rescue efforts will continue around the clock, Luis Pineros, head of government disaster relief agency called the UNGRD, said on Thursday.

The unlicensed mine in central Colombia collapsed on Wednesday, and the authorities have launched an investigation of its owners.

Discovery of the first bodies sapped hopes of anxious relatives of other miners that they might still be found alive.

The workers are believed to be trapped at a depth of 17 metres.

The collapse at the mine on an indigenous reservation in the municipality of Riosucio occurred in its deep shafts, authorities said.

The head of the National Mining Agency told Radio Blu the organisation would investigate the mine, which was in the process of legalisation but was prohibited from digging the shafts that were involved in the collapse.

Investigators say a power cut in the area likely shut off the mine's water pumps, flooding the shafts and leading to the collapse.

The workers at the mine had no formal contract with the company for their high-risk work, the mining agency said in a statement.

Colombia is a major gold producer and business has boomed over the past decade as the price of gold has risen from less than $400 per ounce to almost $1,200.

Source: Al Jazeera and agencies