BOSTON (AP) — Federal transportation regulators ordered a discount bus service between Boston and New York to shut down Thursday, saying its vehicles and drivers were a threat to public safety and that it once dispatched a bus with a large hole in the bottom.

Boston-based Lucky Star's 21 buses did not meet minimum safety standards and that the company failed to properly inspect, repair or maintain the vehicles, U.S. Department of Transportation investigators said. Drivers weren't required to pass drug and alcohol tests and the company did not check documentation of their hours, the investigators also said.

According to the order shutting down the company, it at one point dispatched a bus with a 4-foot-by-2-foot hole in the bottom and significant frame damage. Its buses broke down more than 80 times in just over a year.

Phone and email messages seeking comment were left with Lucky Star.

In March, the discount Fung Wah bus company, which also ran between South Station in Boston and New York City's Chinatown, had its federal license revoked after state officials found problems including cracked bus frames.

Fung Wah had a variety of problems over the years, including a $31,000 fine in 2006 for safety violations after a rollover accident in Massachusetts injured dozens of passengers. In 2005, flames engulfed a Fung Wah bus moments after the passengers were evacuated in Meriden, Conn.

The Department of Transportation said its Federal Motor Carrier Safety Administration has been cracking down on high-risk bus companies since April.

"Companies that disregard the safety rules will not be allowed to operate," U.S. Transportation Secretary Ray LaHood said in a statement.

Other companies shut down in recent months include a tour bus operator involved in a Southern California crash that killed eight people, a Washington, D.C., party bus company and a Niagara Falls, N.Y., tour bus company that officials said required drivers to repair vehicles without ensuring they were qualified to do so.

The department says customers who paid for Lucky Star tickets with credit cards may be entitled to credits from card issuers.