"Violent crime—such as homicide, kidnapping, carjacking, and robbery—is widespread and common in Mexico," the State Department said Wednesday in its notice.

The federal government and State Department have limited capacity to render emergency services to citizens in many places in Mexico. That's because U.S. government employees are restricted or prohibited from going to certain areas, according to the State Department.

"U.S. citizens are advised to adhere to restrictions on U.S. government employee travel. State-specific restrictions are included in the individual state advisories below," the notice said. "U.S. government employees may not travel between cities after dark, may not hail taxis on the street, and must rely on dispatched vehicles, including app-based services like Uber, and regulated taxi stands."

For government workers, they should also avoid traveling alone and in remote areas, according to the bulletin. Federal government employees also cannot drive from the "U.S.-Mexico border to or from the interior parts of Mexico" other than daytime travel in Baja California, a Mexican state that lies south of California, and a select few other areas.

'Do Not Travel'