Guatemalan authorities on Wednesday arrested 18 police officers and a former senior police official for the death last year of three indigenous opponents of a hydroelectric project.

The activists — Luciano Can Jucub, 40, Sebastian Rax, 45, and Oscar Chen, 25 — were killed August 15, 2014 during a police crackdown on protests against the Hidro Santa Rita project in the northern province of Alta Verapaz.

Among those arrested was a former deputy director of operations of the National Civil Police, Pedro Lopez, who faces charges of extrajudicial execution, obstruction of justice, failure to render aid and abuse of authority. The others face similar charges.

Mining activities and the construction of hydroelectric plants in Guatemala have generated strong protests by environmentalists, farmers and indigenous people who see the megaprojects as threats to the environment.

The Hidro Santa Rita project, the target of last year's protests, is backed by Guatemalan and Honduran investors.