Mexican authorities are investigating the killing of seven people near the Arizona border.

The men were shot to death and an eighth man was wounded on a hill called Las Agujas, which is located in an area called Ejido Los Ejemplos, near Sonoyta, close to the border crossing at Lukeville, Sonora's state police said in a news release.

The bullet-riddled bodies were found about 7:30 p.m. Wednesday inside a gray, 2005 Chevrolet pick-up truck.

The lone survivor was Francisco Saúl Hernández Ramírez, according to the Policía Estatal Investigadora, Sonora’s state police. The names of the other men were Jesús Alejandro Virrueta Ramírez, 29, Porfirio Cortes Ramos, 23, José Alexis Niebla García, 22 and Miguel Castillo Lugo, 28. The remaining four have not been identified.

All were believed to have been from the state of Sinaloa.

Police released no information about a motive in the attack.