Federal investigators say the pilot of a Las Vegas police helicopter that crashed on a residential street on New Year's Eve reported a loss of engine power before attempting an emergency landing.

National Transportation Safety Board spokesman Peter Knudson said Monday that a final report on the cause of the Dec. 31 crash could take up to a year to complete.

The impact of the crash sheared the tail from the single-engine helicopter, but officers David Callen and Paul Lourenco escaped serious injury. They were treated at a hospital and released.

An NTSB summary released Wednesday says the pilot tried to maneuver the malfunctioning helicopter toward North Las Vegas Airport before crash-landing on the residential street.

No one on the ground was injured.