The delays began when a high-voltage feeder cable failed at about 5:20 a.m. in Mount Vernon, N.Y., a suburb of New York. Con Edison, the utility serving the New York City area, said another feeder was out on scheduled repair for Metro-North equipment upgrades.
Metro-North first halted service between Stamford and New York's Grand Central Terminal, then provided diesel-powered trains running in both directions once an hour. Crowds of passengers packed the platform at the Stamford station.
Metro-North spokeswoman Marjorie Anders advised commuters to find another way into and out of New York.
"It will be crowded. It will be slow. Seek alternate means," she said in an email.
Irate passengers took to Twitter to vent and the head of a commuter advisory group complained that rail service was disrupted frequently over the summer for needed track work in New York. The incident on Wednesday, though not Metro-North's fault, adds to frustration among commuters, said Jim Cameron, a commuter advocate.
"It means commuters must have a plan B and a plan C," he said.
The state Department of Transportation reported significant traffic congestion on Interstate 95 on Wednesday morning. Traffic eased somewhat by early afternoon - from 20-mile backups to traffic jams a few miles long.
Amtrak, which runs along the same Metro-North corridor, advised passengers that service in the Northeast was operating with "significant delays." Acela Express service was suspended between New York and Boston and service between New York and Washington was operating with delays.
The passenger rail service said it has no estimate for power restoration.