Three people sustained minor injuries Sunday morning after a northbound A train struck an object believed to have been thrown on the tracks and derailed, the authorities said.
One passenger was transported to a hospital and two others were evaluated and declined to be transported, the Fire Department said. About 135 people were on the train.
Sarah E. Feinberg, the interim president of New York City Transit, said the train “came into contact with debris on the roadbed” around 8:15 a.m. as it was pulling into the 14th Street station, causing a wheel to leave the track.
That caused a loss of power to all four tracks and a northbound A train near 34th Street remained in a tunnel, she said. About 125 people aboard that train were safely removed after officials brought in another train and placed an emergency bridge for passengers to walk on.
The authorities suspect that someone threw an object onto the train’s track, causing the accident, a Police Department spokesman, Adam Navarro, said. The police took a 30-year-old man who is believed to be homeless and mentally ill into custody in connection with the derailment and were interviewing him, officials said.
Transit officials at a news conference on Sunday afternoon said they determined that the accident was not related to malfunctioning equipment or inappropriate action by crew members.
Frank Jezycki, the acting senior vice president for subways, declined to comment on specifics about the item that could have derailed the train, but he said it would have been significant.
There was extensive damage to the subway car, the track and four structural steel columns, Mr. Jezycki said. The train’s four front wheels derailed.
“We aim for a normal rush hour for tomorrow morning,” Mr. Jezycki said. “That is the goal. However, we do have a significant amount of work ahead of us, which can only commence once the police investigation concludes.”
Local service was expected to be restored Sunday afternoon and bypass the 14th Street station — where the accident happened — in both directions.
Ashley Southall contributed reporting.