At least 13 workers have been killed and another seven injured in a landslide at an unlicensed mine in southern Colombia, local officials say.

Witnesses described hearing what they said sounded like an explosion at the open-air artisanal gold mine on Wednesday afternoon, moments before the workers below were trapped. But a local official said the deadly landslide had been caused by the mining work.

Emergency workers were able to retrieve the bodies with the help of diggers.

Deadly accidents are not uncommon in Colombia, especially at unlicensed mines where