TIJUANA, Mexico - An American woman was among four people found dead in the Mexican beach town of Playas de Rosarito, near the border with California, officials said yesterday.

The 28-year-old American woman and three men were all shot in the head, assistant Baja California state prosecutor Rafael Gonzalez said. Authorities were still working to identify the men, but they were believed to be Mexican.

Officials were investigating a possible drug link, Gonzalez said.

The bodies were found Sunday in Rosarito, 12 miles south of the California border, and had already begun to decompose, suggesting they had been dead for days, officials said.

Two of the bodies were found in the back of a car with California license plates, and two others were found on the ground near the vehicle, Gonzalez said.

The U.S. Consulate in Tijuana declined to release information on the woman because her family had not yet been notified.

A wave of drug violence has swept Mexico, killing more than 2,500 people last year. Many of the killings have taken place along the U.S.-Mexico border, where cartels waging a bloody turf war with rivals have lashed back against President Felipe Calderon's military crackdown on organized crime.

A retired military major took over the police department in the border city of Ciudad Juarez, across the Rio Grande from El Paso, Texas, yesterday, after the chief resigned following the killings of several of his top officers.

Outgoing Chief Guillermo Prieto had seen drug cartels grow increasingly bold, taking out job ads for drug couriers, shooting rivals in the streets and issuing a hit list that threatened 22 top city police officials.

Of those 22, seven have been killed, three more were wounded and all but one of the others have quit their posts.

Gunmen in Chihuahua state, where Ciudad Juarez is located, yesterday shot and killed the top crime-scene investigator for the state prosecutor's office as he left his home in the town of Hidalgo de Parral. *