DENVER — Prosecutors say a Colorado man has been sentenced to five years in prison for growing thousands of marijuana plants on an island in the Colorado River.

U.S. Attorney Bob Troyer’s office says 33-year-old Santos Ramirez-Carrillo pleaded guilty to conspiracy to manufacture and possess with intent to distribute 50 or more marijuana plants.

According to court records, Ramirez-Carrillo and another man began living and working on the island near DeBeque in May 2017 and worked with other people to grow marijuana in the area, including on federally owned land.

Authorities searched the island in September and arrested Ramirez-Carrillo and another man, Santos Ramirez-Alvarez, at a campsite. Agents found more than 9,100 plants.

Officials say the marijuana grows, which are illegal on federal land, can have a severe effect on the environment.