WASHINGTON (AP) — An air traffic controller making a personal phone call initially failed to warn a small plane of other aircraft in its path and then tried unsuccessfully to contact the pilot, federal safety officials said Friday. Moments later, the plane collided with a tour helicopter over the Hudson River, killing nine people.

The controller handling the plane and his supervisor at Teterboro Airport in New Jersey at the time of last Saturday's accident have been placed on administrative leave pending an investigation by the Federal Aviation Administration.

The National Transportation Safety Board said in a report that the controller — who has not been identified — cleared the single-engine Piper for takeoff at 11:48 a.m. EDT, and then made a telephone call. He remained on the phone, including while further instructing the plane's pilot, until the accident occurred.