Mr. Chen said he then greeted a couple that he knew. But they were going up, to the 36th floor, and when the car for some reason began to go down, they got out on the 32nd floor, Mr. Chen told the police. He continued down until the car got stuck.

In an interview later yesterday, Mr. Chen, 35, said that his calls on the intercom were answered five or six times over the weekend, but that the language barrier was too great. "Sometimes they would respond, sometimes they wouldn't," he said through an interpreter. In one such encounter, he said, "She said something, and I couldn't understand, and she couldn't understand me."

The company that manages the building, however, said the first record that someone had sounded the alarm or used the intercom to call for help was yesterday. "The only indication we had that he was in there was at 4:10 a.m. this morning when he sounded the alarm," said Don Miller, a spokesman for the company, R.Y. Management.

Without disputing Mr. Chen's version of events, detectives were examining all aspects of it, "to make certain that Mr. Chen was not under any duress during the period of his absence," a police official said, declining to elaborate.

The elevator stopped when the selector tape, which tracks the car's position, broke, said Jennifer Givner, a spokeswoman for the city Department of Buildings. Building workers do not know that an elevator is stuck, Mr. Miller said, unless someone calls for help via the intercom or the emergency alarm button inside each cab or is seen on the feeds from the video surveillance camera. Both Mr. Miller and Ms. Givner said all of the monitors had been working.

In fact, an elevator maintenance worker who went into the machine room late Monday afternoon to pick up some gear noticed that the car was not functioning properly and shut off power, but only after calling to the car on the intercom and getting no response, Mr. Miller said. Shutting off the power does not stop the feed from the camera or the operation of the intercom and alarm.

The camera displays most of the car, but there is a blind spot directly under it, the police said. The cameras do not record, relaying live feeds to a security room. Typically, one or two guards monitor feeds from the cameras, Mr. Miller said.