Mexico voiced more anger Wednesday over American agents who killed a teenage boy at a border crossing, as the government called for a review of US rules of engagement.
With Mexican politicians and residents near the border seething, Foreign Minister Patricia Espinosa said Mexico was also "insisting on an exhaustive investigation" into Monday's killing of a 14-year-old boy after a rock-throwing incident near a crossing at Ciudad Juarez.
"There are specific protocols regarding violence on the border," Espinosa said in a statement.
"We are asking for a review of these protocols that allow us to have a clear set of guidelines" for US and Mexican authorities.
She also stressed that officers must act under the principle of "proportionate use of force, depending on the aggression in question."
US authorities have acknowledged the shooting by a US Border Patrol agent as the officer responded to "a group of suspected illegal immigrants from Mexico," and the FBI was heading an investigation. The border agent has been put on administrative leave.
"We regret the loss of life," the State Department said.
The teen, Sergio Hernandez, had been on a "most wanted" list of juvenile smugglers that was compiled by US authorities, Fox News reported Wednesday, citing sources close to the investigation.