(WASHINGTON, DC) -- The U.S. Department of Transportation's Federal Motor Carrier Safety Administration (FMCSA) has shut down a Charlotte-based bus company.  The agency said that Sky Express Inc. violated multiple federal safety regulations.

Sky Express is prohibited from operating in interstate transportation services.  The move comes following a crash in central Virginia on Tuesday involving a Sky Express bus that killed four people.

"Safety is our number one priority," said U.S. Transportation Secretary Ray LaHood. "We will use every resource at our disposal to pursue and remove from our roads unsafe, reckless bus companies."

Virginia State Police blame the crash on driver fatigue. The driver was arrested and charged with reckless driving.

The "out-of-service" order for Sky Express is based on findings by FMCSA in the areas of driver qualification requirements, drug and alcohol compliance, hours-of-service and vehicle maintenance.

"FMCSA will not tolerate passenger bus companies that endanger public safety," said FMCSA Administrator Anne S. Ferro. "Working side-by-side with our North Carolina state law enforcement partners, we took strong action to shut down this unsafe bus company."

However, according to FMCSA records, violations by Sky Express have been documented in the last two years. As recently as May 11, 20011 FMCSA recommended shutting down the company, but a required 45 day waiting period prevented the action from taking place.