Amtrak suspended most of its high-speed Acela service today to inspect the trains for cracks in shock absorbers beneath their locomotive cars.
Amtrak found cracks below three locomotives. Two trains that passed the inspection Monday night are expected to be in service.
Inspections are continuing on Amtrak's other Acela Express trains, which operate between Washington, D.C., New York and Boston.
Passengers will be credited for the difference in ticket prices between Acela Express and the trains they do take.
On a typical weekday, about 40,000 people ride Amtrak in the Northeast Corridor, which also services the Acela Regional and Metroliner trains. Of that number, more than 10,000 use Acela Express.
The first cracked yaw damper bracket was discovered Monday during a periodic maintenance inspection. Each power car has four yaw dampers that prevent swaying at high speeds, which could accelerate wear and tear to rails and train wheels. A yaw damper that broke loose could cause serious damage to the train's underside.