Mexico City, Mexico (CNN) -- Mexican President Felipe Calderon is scheduled to make his third visit in a little over a month Tuesday to the troubled border city of Juarez, where three people associated with the U.S. Consulate were killed over the weekend.
Ciudad Juarez is the most violent city in Mexico, with more than 2,600 drug-related deaths in 2009. No official numbers are available, but more than 400 killings have been reported in local media this year.
The city, long the focal point of Calderon's war on drug cartels, came to renewed prominence after the January 31 killings of 15 people, most of them students with no ties to organized crime. The incident sparked outrage across Mexico.
Calderon visited Juarez twice within a one-week period in mid-February, meeting with local officials and residents.
This weekend's deaths of a pregnant woman and two other people connected with the U.S. Consulate renewed attention to the blood-soaked city.
Juarez Mayor Jose Reyes Ferriz told CNN on Monday that the killings were carried out by a local gang known as Los Aztecas, which is allied with the Juarez Cartel. No arrests have been made.
"We know that the U.S. citizens were targeted," Reyes said Sunday, saying a police officer witnessed the shooting. "We know they were chasing them. We know they wanted to kill them."
Two of the victims were U.S. citizens: a four-months-pregnant employee at the consulate and her husband, who was a jailer in El Paso, Texas, right across the border from Juarez, U.S. and Mexican officials said. The couple's 10-month-old child, who was in the vehicle, was not injured, Reyes and other officials said.
The child has been turned over to U.S. consular officials, according to Reyes. The couple lived in El Paso, the State Department said.
The third victim was identified as the husband of a Mexican employee of the consulate. His wife was not traveling with him, but two of their children were in the car and were wounded, officials said.
All the victims had left a birthday party at the U.S. Consulate in Juarez on Saturday when they were attacked, Reyes and State Department spokesman P.J. Crowley said Monday. The husband and wife who were killed, identified as Arthur Redelfs, 34, and Lesley Ann Enriquez, 35, were on their way home to El Paso, Crowley said.
Redelfs was a 10-year veteran of the El Paso County Sheriff's Office, according to Jesse Tovar, a spokesman for the department.
The third victim was identified as Jorge Alberto Salcido Ceniceros, 37, a state police officer who was married to a Mexican employee at the U.S. Consulate.
Their two children, ages 4 and 7, were transported to a hospital for treatment of their wounds, the attorney general's office said. Salcido's wife was traveling in another vehicle, which was not attacked, Reyes said.
"These appalling assaults on members of our own State Department family are, sadly, part of a growing tragedy besetting many communities in Mexico," U.S. Secretary of State Hillary Clinton said in a statement Sunday night. "They underscore the imperative of our continued commitment to work closely with the Government of President Calderon to cripple the influence of trafficking organizations at work in Mexico."
The U.S. State Department authorized the temporary relocation of employees' families working in border-area consulates.
The families of employees at U.S. consulates in Tijuana, Nogales, Ciudad Juarez, Nuevo Laredo, Monterrey and Matamoros are allowed to leave for a period of 30 days as part of the temporary relocation program "in response to an increase in violence along the Mexican side of its border with the U.S.," State Department spokesman Fred Lash told CNN.
The authorization can be renewed after 30 days, depending on a review, Lash said, adding that this was not a mandatory evacuation.
The announcement was part of a warning to U.S. citizens regarding travel to Mexico.
The warning urges U.S. citizens to delay nonessential travel to parts of the states of Durango, Coahuila and Chihuahua, where Juarez is located, because of "recent violent attacks." U.S. government employees are currently restricted from traveling to all or parts of these three states.
Attacks include the kidnapping and killing of two resident U.S. citizens in Chihuahua, the warning states.
"Some recent confrontations between Mexican authorities and drug cartel members have resembled small-unit combat, with cartels employing automatic weapons and grenades," the warning says. "During some of these incidents, U.S. citizens have been trapped and temporarily prevented from leaving the area."
The Mexican government has not released official figures, but national media say 7,600 people lost their lives in the war on drugs in 2009. Calderon said last year that 6,500 Mexicans died in drug violence in 2008.
No official figures are available, but unofficial tallies this year say more than 16,000 people have been killed since Calderon declared war on the cartels after assuming office in December 2006.