MEXICO CITY (AP) — Mexican officials say three LGBTQ activists have been shot dead and left along a highway in the troubled southern state of Guerrero.

Guerrero security spokesman Roberto Alvarez says the bodies were found Sunday on a road between Taxco and Cuernavaca with bullet wounds to the head.

Alvarez said Tuesday that evidence and witness testimony suggest the killings may have been linked to extortion. Four people were arrested in possession of weapons and drugs, and one is suspected in the killings.

The victims were identified as Ruben Estrada, a gay community leader in the town of Taxco, and activists Carlos Uriel Lopez and Roberto Vega.

Guerrero is a flashpoint for drug gang violence, and Taxco is a popular tourist destination famous for its cobblestone streets and artisanal silver industry.