Ricardo Valles (right) has said he was a lookout for the gang, authorities say
A suspect in the murder of three people with links to the US consulate in Ciudad Juarez has said the target was a US prison guard, Mexican officials say.
Authorities said Ricardo Valles, an alleged member of the Barrio Azteca gang, told them he acted as lookout.
The guard and his wife, who worked at the consulate, were shot dead on 13 March as they left a party in Juarez.
A Mexican man married to another consulate employee was killed as he left the same party in a similar car.
Arthur Redelfs worked as a prison guard just across the border at the El Paso County Jail.
He and his wife Lesley Enriquez, both US nationals, were shot dead after attending a birthday party in Ciudad Juarez.
Their seven-month-old daughter was found crying in the back of their car.
Mr Valles told investigators that a gang leader had ordered him to locate "the white sport utility vehicle" used by Mr Redelfs.
He said that had followed the car carrying the couple until gang members told him to back off, after which the Americans were shot.
At about the same time, Mexican Jorge Salcido, who was driving a similar white vehicle, was also shot dead.
The exact motive of the killings remains unclear.
One theory investigators are working on is that the shootings may have been an act of revenge against Mr Redelfs.
Barrio Azteca members operate and are jailed on both sides of the border.
Another theory is that the killings were a case of mistaken identity and that in fact none of the three victims was the target.
"The information the suspect has given is still being verified, so the authorities are not releasing other information on other probable participants in the double shootings and their probable motive," a statement from the Chihuahua state prosecutor's office said.
FBI agents were sent to Ciudad Juarez to work alongside Mexican officials in the murder investigation.
More than 2,500 people died last year in Ciudad Juarez, one of the focal points of Mexico's illegal drugs trade.
US Secretary of State Hillary Clinton, who was in Mexico as part of a high-level US delegation last week, pledged increased support for Mexico in the fight against drug gangs.
She said more would be done to cut US demand for drugs and the flow of profits and guns into Mexico.