Stessel said the mechanical problem that caused the train to break down was a random occurrence, and that Metro had adequate staff and responded quickly. But it took time to disable the brake lines on a fully loaded 8-car train and move it off the track, he said.
"It just happened at a bad time and a bad place," Stessel said. The resulting delays, he said, were "one of the challenges of operating on what is a two-track railroad."
Stessel said transit officials occasionally close stations to cope with crowding, as they did in August 2011, when a rare earthquake caused a sudden mass exodus from downtown Washington.
"It's something that we're prepared to do, based on crowd conditions, on any day," Stessel said.
Even stations that remained open grappled with major crowding. At Farragut West, crowds lined up to buy fare cards, clogging the entry to the platforms.
Earlier Monday, there were long lines to get out of Federal Center SW, a small station with a single point of entry. More than 100,000 tickets to the ceremony listed that station as the closest one. That went against Metro's advice for passengers to be flexible about which stops to use. Some trains didn't stop there because there wasn't enough room on the platform for more passengers to disembark.
The experience was frustrating to Thia Golson of Alexandria, Va., who had to double back after her train bypassed the station without warning.
"There was no announcement on the train," she said.
Associated Press writers Jessica Gresko, Richard Lardner and Eric Tucker contributed to this report.