A private helicopter is believed to have crashed in waters off Anna Bay after going missing from Williamtown Airport's flight radar on Friday night.
NSW Police were advised at about 6.30pm that an aircraft had "faded off the radar" near Anna Bay, a police media spokeswoman said.
Officers from Port Stephens Police District and the Marine Area Command, along with Marine Rescue and other aerial support, are conducting a large scale search of the area.
The police spokeswoman could not confirm what type of aircraft was involved, or where it had come from, but the Australian Maritime Safety Authority has since confirmed it was a private helicopter.
An AMSA spokesman said initial reports suggested the helicopter was out of Coffs Harbour and four people were on board.
Newcastle Herald photographer Marina Neil is at Birubi beach in Anna Bay where a police boat, helicopter and other resources are searching the water more than a kilometre out to sea.
The Australian Maritime Safety Authority, which is coordinating the search, deployed its search and rescue aircraft out of Melbourne and it is conducting flyovers of the area.
A Westpac Rescue Helicopter Service spokesman said one of its helicopters was in the air as well.
"Our aircraft is still up in the air in that area after the report of an aircraft crash," he said at about 9pm.
"There was a call through air traffic control at Williamtown, that they'd lost contact with an aircraft."
The NSW Incident Alerts page on Facebook said debris had "been spotted by Marine Rescue crews during the search". That information is yet to be confirmed.
The Bureau of Meteorology issued a severe weather warning on Friday night for the region where the aircraft lost contact, predicting damaging, locally destructive winds with peak gusts in excess of 125km/h and average gusts of 80km/h-90km/h.
It said a strong cold front from the west was sweeping across the state, generating the vigorous westerly winds.
