U.S. President Barack Obama is outraged over the suspected murder of three people with ties to the U.S. Consulate in Mexico over the weekend, a government spokesman has said.

Soldiers stand guard at a crime scene where the crashed car of a U.S. Consulate employee sits in Ciudad Juárez, Mexico, on Sunday. (Associated Press)

The three – a consulate employee and her husband, both U.S. citizens, and another consulate employee with Mexican citizenship – were killed by suspected members of a drug gang in Ciudad Juárez on Saturday.

The U.S. will join Mexican authorities in working "tirelessly to bring their killers to justice," National Security Council spokesman Mike Hammer said Sunday.

Mexican President Felipe Calderón also expressed outrage and promised a fast investigation to find those responsible.

Mexican authorities suspect the gang members because of "information exchanged with U.S. federal agencies," according to the joint mission of soldiers and federal police overseeing security in Ciudad Juárez.

Police offered no information on a possible motive in the slayings. U.S. State Department spokesman Fred Lash said only that the three people who died had been at a party before the attacks occurred minutes apart Saturday afternoon.

The killings took place in Ciudad Juárez, where a rash of violence has left several American citizens dead in recent years. (CBC)

A pattern of violence

The killings are the latest in a rash of violence along Mexico's border with Texas.

Several U.S. citizens have been killed in Mexico's drug war, most of them people with family ties to Mexico. It is rare for American government employees to be targeted, although attackers hurled grenades at the U.S. Consulate in the northern city of Monterrey in 2008.

The State Department authorized U.S. government employees at Ciudad Juárez and five other U.S. consulates in northern Mexico to send family members out of the area because of concerns about rising drug violence.

Lash said the decision was based not only on Saturday's killings, but also on a wider pattern of violence and threats in northern Mexico in recent weeks.

With files from The Associated Press