Cocaine farmers in Colombia are leaving the drug business and moving into illegal gold-mining.

Authorities have shut down scores of mines in the northwestern province of Cordoba in a crackdown on illegal mining that started in September. About 400 police took part in the sweep.

Communities near the unregulated mines suffer from the "improper use of mercury and other contaminating substances" found in soil and bodies of water, officials said.

Al Jazeera's Monica Villamizar reports from Norosi.