Yellow buoys that a New York police officer said are suspending a helicopter that crashed into the East River float next to a NYPD police boat at a pier in New York on Sunday, March 11, 2018. The helicopter crashed into New York City's East River Sunday night and flipped upside down in the water, killing at least a few people aboard and leaving some others in critical condition, officials said. (AP Photo/Andres Kudacki)

NEW YORK | A pilot whose helicopter went down in Manhattan’s East River, killing five passengers, says in an emergency radio transmission that he had engine failure.

The pilot is heard saying “Mayday, mayday, mayday” during the crash on Sunday night.

The person at the other end of the transmission had trouble making out what the pilot was saying.

The pilot reported “an engine failure over the East River” and referenced a hotel.

The National Transportation Safety Board dispatched investigators on Monday.

The charter helicopter was hired for a photo shoot.

The pilot freed himself and was rescued by a tugboat. Emergency divers had to remove the passengers from tight harnesses while they were upside down.