Mexico's governmental human rights commission recommended that prosecutors open criminal investigations into the deaths.
The incident happened during the repairs of the water network.
Patricia San Martín Núñez and her daughter, Elsa Veronique Delplace San Martín, are the niece and grand-niece of ambassador Ricardo Núñez.
The victim was a 21-year-old man.
A 45 year-old man drowned in Santo Tomás Chiconautla.
Mexico is objecting to a U.S. decision to negatively certify it for not doing enough to reduce the deaths of endangered sea turtles in fishing nets.
The decomposing bodies were found in plastic bags in their house in Tijuana.