Washington ? Amtrak shut down its high-speed Acela trains Friday after maintenance crews discovered cracked brake parts on several of its cars, and officials of the rail line said the trains could be out of service for months.

The problem was found on a handful of Acela cars during a routine brake inspection late Thursday at a Washington maintenance yard. A more extensive inspection of all 20 Acela trains Friday found that more than one in five brake rotors on the trains were defective. Amtrak officials said they did not know whether the problem could have caused an accident.

“I think it is safe to say that this is how you would want to find out about the problem, as opposed to the alternative,” said Bill Crosbie, Amtrak’s chief operating officer.

The Acela cancellations came one day after the Bush administration released its plans for restructuring Amtrak by breaking up the rail line and turning it over to the states.

Crosbie said it could be two months or more before all the Acela trains were running again. Acela tickets are among the most expensive available on Amtrak, and Crosbie said the loss of Acela revenue surely would hurt the rail line.

The cancellation of Acela trains between Washington and Boston forced as many as 10,000 riders to find other trains or other ways to get to their destinations. Although Amtrak pressed five additional regional trains into service, they clearly were not enough. Amtrak trains Friday were crowded and many passengers had to stand.

At Washington’s Union Station, unusually long lines snaked almost the length of the station as passengers lined up to board the 3:05 p.m. EDT regional train to Philadelphia and New York.

“It has a ripple affect on passengers,” said Norman Blain of Philadelphia, who was about to board a train for the trip home.

Amtrak has suspended its high-speed Acela train service, saying that it found cracks in brake components during routine tests and inspections of cars in the premium-priced train service that connects Boston, New York and Washington. Two Acela trains sit in a train yard Friday in Washington, D.C.

Amtrak runs 15 Acela weekday round trips between New York and Washington and 11 between New York and Boston. The Acela is the most advanced of Amtrak’s trains, with a top speed of 150 mph. Acela service was canceled for several weeks in the summer of 2002 because of equipment problems.

The shutdown announcement triggered concern that Amtrak’s strained finances and constant battling with the White House and Congress over its budget had contributed to the problem.

Crosbie said Friday he was confident that lack of maintenance was not the cause of the problem, although he said the rail line would have a better picture next week of what went wrong.