The Mexican Foreign Ministry expressed its "deepest concern for this tragic accident" on Saturday and said it had asked Mexican consular officials in the US to demand an investigation.
The ministry said it was calling on American authorities to review its methods of enforcing immigration laws, which it said "have caused, over a few days, two very grave incidents involving Mexican citizens."
The crash came less than a week after a truck filled with illegal immigrants was chased over 80 miles. The chase ended with the videotaped beating of two illegal immigrants by Riverside County sheriff's officers. Thousands of demonstrators jammed the streets of Los Angeles on Saturday to protest against the beatings.
The crash came after agents had followed the truck for about 12 miles. The truckdriver lost control on a curvy road and overturned in a gully.
All seven of the men who were killed were crammed into the smashed cab, said Johnny Williams, the chief of the US Border Patrol in San Diego. "It was a grisly, grisly scene," he said.
The identities of the dead and injured were not immediately known. But Mr Williams said there was every indication that the men were illegal immigrants.
"If we are able to identify the smuggler as one of the survivors, I'm pulling out all the stops to prosecute him," he said. "[This incident] ... shows the disregard these smugglers have for human life and usually, their own countrymen. They're preying on them like leeches."Reuse content