PHILADELPHIA (AP) — Concerns over vehicle and driver safety led federal regulators to shut down a bus company that took passengers from several cities to New York City's Chinatown.

U.S. transportation officials have ordered Double Happyness Travel Inc. to immediately cease operations, deeming the company's bus service "an imminent hazard." Investigators said they found numerous violations of rules on vehicle maintenance and driver safety, including drug and alcohol testing and records on how long drivers were working.

Double Happyness runs buses from Albany, Baltimore, Md., and Wilmington, Del., to midtown and Chinatown in New York City. Authorities did not cite any accidents involving the company in its press release.

The company did not immediately return a message Thursday at its corporate office in Huntingdon Valley, near Philadelphia.

The Federal Motor Carrier Safety Administration said it has doubled inspections and safety reviews of the nation's 4,000 bus lines in the past five years.

Low-priced bus service has exploded in popularity in recent years, and there have been several deadly crashes along the East Coast that led to criminal charges and other repercussions.

The driver of a tour bus involved in a March crash that killed 15 people returning from an overnight gambling trip was later indicted on manslaughter charges in New York City. The World Wide Travel bus ran off Interstate 95 at daybreak as it was returning to Manhattan's Chinatown from an overnight trip to the Mohegan Sun casino in Uncasville, Conn.

In September 2010, a Megabus driver missed a turn late at night and failed to clear a low railroad bridge near Syracuse, N.Y., after missing 12 warning signs, some with flashing lights, before the bus slammed into a low bridge, killing four people and seriously injuring others. The driver is charged with negligent homicide, while at least one civil suit is pending against parent company Coach USA.

In June, federal transportation officials shut down a bus company involved in a fatal crash on the Pennsylvania Turnpike after finding the two drivers involved never took required drug tests and falsified records. The bus, run by Mr. Ho Charter Service of Bethlehem, rear-ended a tractor-trailer that month in western Pennsylvania, killing a driver and injuring two dozen Asian tourists.