Nariño's government said an additional seven people were injured in the mining accident near the small town of Santa Barbara de Iscuande, adding that search efforts had ended on Monday night.
"This emergency once again highlights the risks associated with informal mining," the statement said.
"In less than three months, two collapsed mines in Nariño have killed 27 people."
Santa Barbara de Iscuande is surrounded by dense rainforest and can only be reached by boat or small aircraft, which make it difficult for aid workers to reach the area.
"Entire families have been killed in this regrettable accident. It is very sad," said Nariño's governor, Luis Alfonso Escobar.
Hundreds of small mines in Colombia operate without government permits and some are controlled by rebel groups.
Besides being difficult to reach, Santa Barbara de Iscuande also faces security problems.
Two rebel groups reportedly operate in the area, including the Jacobo Arenas Block, a group led by former members of the Revolutionary Armed Forces of Colombia who refused to join a 2016 peace deal with Colombia's government.
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