BOGOTA, Colombia (AP) — Colombia's armed forces have arrested 59 people in a major crackdown on illegal mining in the Amazon rainforest dominated by leftist rebels.

The Defense Ministry on Monday said that 600 special forces supported by aircraft and inflatable boats had carried out the sweep in an area covering more than 700 square kilometers (270 square miles) in five undeveloped eastern provinces where metals such as tungsten, gold and coltan are illegally extracted at great risk to the environment.

Among those arrested are 12 members of the Revolutionary Armed Forces of Colombia. The Defense Ministry said mining activity in the region generated more than $8 million a month for the rebels and said the operation was the biggest blow against illegal mining in a decade.