The helicopter that crashed into New York City's Hudson River on Thursday, killing all six people on board including three children, lacked flight recorders, the National Transportation Safety Board said.

Officials have released the names of the victims in Thursday's deadly helicopter crash. The cause is still not known.

The helicopter that plunged into the Hudson River on Thursday and killed all six people aboard was on its eighth sightseeing trip of the day and lacked a flight data recorder, federal investigators said.