CIUDAD JUAREZ, Mexico (Reuters) – The killing of three people linked to the US consulate in Mexico’s bloodiest drug war hotspot has thrown President Felipe Calderon a major test as he heads to this border city today to try to contain spiraling violence.

Suspected drug hitmen killed an American woman working at the consulate in Ciudad Juarez, just over the border from El Paso, Texas, and her US husband on Saturday as they left a children’s birthday party. A Mexican man married to another consulate employee was killed around the same time in another part of the city after he and his wife left the same event.

The FBI joined Mexican authorities in the investigation of the murders, while US officials downplayed suggestions that US diplomats had been targeted in the attacks.

The White House expressed outrage over the murders and pledged to continue supporting Mexico’s fight against ruthless gangs smuggling narcotics into the United States.

“The tragic murders over the weekend underscore the imperative of our continued commitment to work closely with Mexican authorities to take down the drug trafficking organizations,” National Security Council spokesman Mike Hammer.

Violence has exploded in recent months in Ciudad Juarez as rival drug gangs struggle for control over the city, a hotspot in Mexico’s three-year-old drug war.

The deployment of thousands of troops by Calderon, who has staked his presidency on beating back the drug cartels, has failed to stop the killing of more than 4,600 people over two years in the Ciudad Juarez area.

Calderon was already scheduled to visit Ciudad Juarez before the consulate murders added to outrage at the slaying in January of 15 people, mainly teenagers, at a party.

Many residents blame Calderon for fanning violence that has provoked an exodus of people from the manufacturing city and forced some U.S companies to freeze investment in factories.

“Calderon’s strategy is not working, but he doesn’t want to change it. He believes in the military and so we are at this impasse,” said security expert Pedro de la Cruz at the National Autonomous University of Mexico. “We are going to witness a lot more murders for the time being,” he added.

An FBI official in El Paso said there was still no evidence the consular killings were drug-related. “There is no information that indicates that the victims were directly targeted due to their employment at the consulate,” said FBI Special Agent Andrea Simmons.