The 20-year-old man was arrested by members of the same unit, the GIGN, and taken into custody on Saturday over last month’s deadly shooting, Yves Le Clair, the prosecutor for Cayenne, told AFP.

The suspect, a Brazilian, was arrested after having indicated that he was ready to surrender, Le Clair added.

The slain gendarme, 35-year-old Arnaud Blanc, was part of a joint operation with the French army against illegal gold mining when he was shot dead on March 25.

Investigators’ preliminary findings suggest the suspect is a member of a gang involved in illegal gold mining, although not himself a miner.

French authorities fear the illegal gold extraction is a major source of pollution into sensitive water systems.

Last year, French authorities carried out more than 1,000 patrols in the Guiana forest against illegal gold mining, seizing 59 kilograms (130 pounds) of mercury and five kilograms of gold, according to a report from local authorities.

Local mining operators say 10 tonnes of gold are illegally extracted from French Guiana each year by unauthorised gold miners known locally as “garimpeiros”.

French Guiana is one of several significant overseas territories which remain part of France and span South America to the Indian Ocean to the Pacific.