WASHINGTON — A Metro train derailment on a downtown stretch of the Red Line on Monday morning was probably caused by a broken rail, officials said.

The agency said a train with 63 passengers aboard derailed as it passed over a section of defective tracks around 6:30 a.m. One passenger was evaluated for shortness of breath, but there were no serious injuries, officials said.

Three cars from the rear of the train came off the tracks, officials said, and the passengers were herded through the tunnel after an estimated 90-minute wait.

The early-morning derailment on a busy section of the system downtown raised new questions about the millions invested in the yearlong SafeTrack maintenance program, and efforts to raise hundreds of millions more to improve the safety and reliability of the system.

The cleanup, meanwhile, was likely to impact the Tuesday morning commute.

The derailment happened about 6:30 a.m. after the train left Farragut North station. Passengers described a sudden jolt that felt like extreme airline turbulence.

WASHINGTON POST