Three people connected to the US consulate in the Mexican border city of Ciudad Juarez have been killed, the White House has said, BBC reported.
They include a consulate employee and her husband, both American, and the Mexican husband of another employee.
The White House said President Barack Obama was "outraged" by the murders and would work with Mexican officials to bring the killers to justice.
Mexico is battling a drug war that has killed some 18,000 people since 2006.
The three victims were killed in drive-by shootings on Saturday afternoon, a US official told the BBC on condition of anonymity, citing privacy considerations.
The White House statement did not provide any details of the incident in Ciudad Juarez, where more than 2,600 people were murdered last year in drug-related violence.
Meanwhile, the State Department has authorised government employees at six US consulates in northern Mexico to send their family members out of the area over concerns about rising drug-related violence.
The six consulates are in the border cities of Tijuana, Nogales, Ciudad Juarez, Nuevo Laredo, Monterrey and Matamoros.
The department said in a statement Sunday that recent violent attacks have led the US Embassy in Mexico City to advise American citizens to delay unnecessary travel to parts of the Mexican states of Durango, Coahuila and Chihuahua.