The bodies of 3 LGBT rights activists were found Sunday along a highway in the southern Mexican state of Guerrero.

According to the AP, the bodies were found on a road between Taxco and Cuernavaca.

The bodies had bullet wounds to the head.

The victims were identified as activists Ruben Estrada, Carlos Uriel Lopez and Roberto Vega.

Roberto Alvarez, a security spokesman for Guerrero, said Tuesday that the killings may have been linked to extortion. A suspect has been arrested.

Last year, the U.S. State Department warned Americans not to travel to Guerrero, where gang-related violence has been on the rise. The advisory placed Guerrero in the department's highest risk category.