Update (4:57 p.m. EDT): Reuters is now reporting that the attack on the U.S. embassy vehicle came from Mexican federal police officers who mistook it for one driven by kidnappers they were pursuing. But the Associated Press's latest update says the attack may have come from police or it may have come from other, "unidentified gunmen" who were pursuing the embassy vehicle, and with whom police exchanged fire. The two U.S. employees were police trainers, according to Reuters, but CNN reports that there was confusion about their identity: "The Mexican official said three Mexican marines were wounded, some Mexican reports said two of the wounded were Americans, and a U.S. government official said the three victims were Americans."

Original: For all the violence that plagues Mexico it's rare U.S. officials are targeted, but Friday's attack on a U.S. embassy vehicle, which injured two U.S. government workers, sure sounds deliberate. Not only did the Toyota sport diplomatic plates, but it "was riddled with bullets, most concentrated around the passenger-side window, indicating possible involvement by experienced gunmen," The Associated Press' Michael Weissenstein reports. Two passengers were hospitalized "one with a wound to the leg and the other hit in the stomach and hand," according to Weissenstein.

So far, The AP provides the only real account so far of what happened. The U.S. embassy hasn't commented on the shooting on a highway outside of Cuernavaca, south of Mexico City. Weissenstein cites a "law enforcement official" in his report, but specifies that the two Americans were not with the Drug Enforcement Agency or the FBI. A Mexican Navy captain was apparently also in the vehicle, but he escaped unharmed. Last month, a U.S. immigration agent was shot and wounded near the Texas-Mexico border, and last year a roadside attack killed one immigration agent and wounded another. But compared to the numerous attacks on Mexican police seen in the recent drug violence, U.S. law enforcement operating there have been relatively safe.