The federal government has posted signs along a major interstate highway in Arizona, more than 100 miles north of the U.S.-Mexico border, warning travelers the area is unsafe because of drug and alien smugglers, and a local sheriff says Mexican drug cartels now control some parts of the state.

The signs were posted by the Bureau of Land Management (BLM) along a 60-mile stretch of Interstate 8 between Casa Grande and Gila Bend, a major east-west corridor linking Tucson and Phoenix with San Diego.

They warn travelers that they are entering an "active drug and human smuggling area" and they may encounter "armed criminals and smuggling vehicles traveling at high rates of speed." Beginning less than 50 miles south of Phoenix, the signs encourage travelers to "use public lands north of Interstate 8" and to call 911 if they "see suspicious activity."

Pinal County Sheriff Paul Babeu, whose county lies at the center of major drug and alien smuggling routes to Phoenix and cities east and west, attests to the violence. He said his deputies are outmanned and outgunned by drug traffickers in the rough-hewn desert stretches of his own county.