A drug cartel was behind the assassination of a U.S. consular worker in Mexico, local government said Sunday.

According to shared information between Mexican and U.S. federal agencies, the attackers were believed to be from a gang known as "the Aztecas," which works for the Juarez Cartel, the Chihuahua state government said in a press release.

A female employee of a U.S. consulate in Mexico, along with her U.S. husband and the husband of another consular employee, were killed by murderers Saturday afternoon when they were driving at different locations in the city of Ciudad Juarez.

U.S. President Barack Obama was "deeply saddened and outraged" by the murders, a White House spokesman said shortly after the news reached Washington.

Ciudad Juarez is notorious for drug-related violence, which killed some 2,600 people last year.

"We will continue to work with Mexican President Felipe Calderon and his government to break the power of the drug trafficking organizations that operate in Mexico and far too often target and kill the innocent. This is a responsibility we must shoulder together," said a White House spokesman.

In light of the situation in Mexico, the U.S. State Department has issued travel warning to inform Americans traveling to and living in Mexico of concerns about the security situation in Mexico.

The State Department has also authorized the departure of the dependents of U.S. government personnel from U.S. consulates in the northern Mexican border cities of Tijuana, Nogales, Ciudad Juarez, Nuevo Laredo, Monterrey and Matamoros until April 12.