Two agents who were attached to the embassy in Mexico city were attacked while on the way to Monterrey, killing one and wounding another.

New York Times:

The agent who was killed was identified as Jaime J. Zapata. He joined the agency in 2006 and served in Laredo, Tex., before a recent assignment to Mexico City. The name of the other agent was not released, but a statement from the immigration and customs agency said he was in stable condition.

It was the first time that an employee of the immigration and customs agency had been wounded or killed in the line of duty in Mexico, American officials said.

Typically American immigration agents are involved in major investigations of trafficking, in conjunction with Mexican law enforcement. And on Tuesday, the American agents were clearly driving into dangerous territory. The police in San Luis Potosí State said the attack occurred on a main highway about midway between Mexico City, the capital, and Monterrey, the same highway where, a month ago, a group of armed men clashed with the federal police in a running battle that left five presumed criminals dead.

The American agents' destination, Monterrey, a large, wealthy city two hours from McAllen, Tex., has become an epicenter of drug gang battles over the past year as the Gulf Cartel and an offshoot, the Zetas, have fought for control of smuggling routes.

American and Mexican authorities have warned that roads throughout the area are rife with false checkpoints run by drug cartel gunmen, and recent victims have not been limited to rivals. This week, a senior police intelligence official was found dead in his burning armored car in Monterrey.