MEXICO CITY: Drug violence may be behind the killing of four taxi drivers in the picturesque central Mexican town of San Miguel de Allende, a popular tourism destination that is home to thousands of American retirees, authorities said on Thursday.

Mayor Ricardo Villarreal said that while the investigation into the Wednesday night slayings was continuing, the bloodshed appeared to be a “score settling” within the world of street-level drug sales.

Villarreal said in an interview with Radio Formula that because San Miguel is a tourist destination, it is prone to small-scale drug sales.

Saying the city remains a safe place, he said the four slain taxi drivers were targeted, not the victims of random attacks. He said the drivers apparently were all called to the location on the town’s outskirts where they were killed in their cabs.

A statement from the city said two other men were wounded.

Mexico has struggled with increased drug gang violence in some of its most popular tourism spots. Killings and attacks have occurred recently in Cancun, Zihuatanejo and Los Cabos, though the attacks have not targeted tourists.