Citing imminent safety hazards, federal officials ordered 26 companies on Thursday to stop operating many of the inexpensive buses that pick up passengers at curbsides all over Manhattan’s Chinatown and haul them to other cities up and down the East Coast.

The crackdown was the most sweeping action ever taken against American passenger-bus operators and was intended to chasten other low-budget companies that might try to evade safety regulations and the relatively small pool of inspectors who enforce them, Transportation Secretary Ray LaHood said.

“Shutting them down will save lives,” Mr. LaHood said at a sidewalk news conference in Chinatown.

The 26 companies were affiliated with three “unscrupulous” networks of bus operators that ignored federal rules and, when they were caught, simply changed names and continued operating, said Senator Charles E. Schumer, Democrat of New York, who was also in Chinatown.

On paper, only four of the companies were based in New York, but in reality, much of their business involved shuttling about 1,800 passengers a day between Manhattan, Boston, Washington and places as far south as Florida.