An American woman was among four people found dead in the Mexican beach town of Rosarito, near the California border, assistant Baja California state prosecutor Rafael Gonzalez said.
The 28-year-old woman and three men were shot in the head, he said. The unidentified men were believed to be Mexican.
The U.S. Consulate in Tijuana declined to release information on the woman until relatives were notified.
Officials were investigating a possible drug link, Gonzalez said. The four, found Sunday, appeared to have been dead for days, officials said.