WASHINGTON, May 15, 2013 /PRNewswire-USNewswire/ -- The U.S. Department of Transportation's Federal Motor Carrier Safety Administration (FMCSA) has ordered Mexico-based passenger carrier Autobuses Zacatecanos, LLC, to cease U.S. operations and revoked the firm's authority to provide passenger service within the United States, declaring that its drivers and vehicles pose an imminent hazard to public safety. Autobuses Zacatecanos, LLC, operates a fleet of four buses and primarily provides service between Zacatecanos, Mexico, and Los Angeles, Calif. The company has also operated occasional routes from Mexico to Denver, Phoenix and Chicago. "Our safety investigators and inspectors are working diligently to keep the traveling public safe," said U.S. Transportation Secretary Ray LaHood. "Bus and truck companies that fail to adhere to our safety regulations will not be allowed on our highways and roads. We demand that safety come first." This action marks the sixth shutdown of a passenger carrier following the deployment last month of more than 50 specially trained "Quick Strike" safety investigators targeting high-risk passenger carriers. In the past three weeks, FMCSA investigators have shut down bus companies in the District of Columbia, Georgia, Ohio, New York and Utah. Since the beginning of 2013, FMCSA has shut down a total of 13 bus companies and seven trucking companies. The agency has also declared three commercial driver's license holders as imminent hazards, blocking them from operating in interstate commerce. "Every bus company that operates in the U.S. must comply with the same safety regulations, and if they do not, we will take immediate action," said FMCSA Administrator Anne S. Ferro. "We have zero tolerance for putting the lives of passengers and drivers at risk. All travelers on our roadways are entitled to reach their destination safely." During an investigation of Autobuses Zacatecanos, FMCSA safety investigators found the company failed to ensure that its vehicles were systematically and properly inspected, repaired and maintained. Onsite inspections of Autobuses Zacatecanos' four buses revealed such numerous and serious safety violations that all four vehicles were immediately declared out of service. In addition, each of the buses was found to have inadequate and/or obstructed emergency exits.