A light plane carrying a pilot and photographer is yet to be found after crashing into waters off southeast Tasmania.
The pair were capturing footage of boats competing in the Sydney to Hobart yacht race when the aircraft plunged into the sea about 6.20pm on Monday.
The crew on board race competitor Mistraal witnessed the crash and watched the Cessna's tail disappear beneath the waves.
"Mayday, mayday, mayday ... we've a plane in the water," came the radio call from cruiser Mistraal as she rounded the Tasman Peninsula bound for the finish line.
Police will hold a press conference on Tuesday morning to provide an update on efforts to find the plane, which includes search crews in the air, at sea and on land.
An oil slick has been found in the area and two helicopters are sweeping the crash zone.
There are three police boats and coastal foot patrols are being made by SES volunteers.
Seven race yachts diverted to help search for the plane.
When Mistraal made it to Hobart about 11pm on Monday, her crew declined to comment on the plane crash.
Owners of the single-engine Cessna 172, Airlines of Tasmania, confirmed the aircraft went down in the vicinity of Port Arthur.
"We are working with all relevant authorities and providing as much assistance as we can to the Tasmania Police," managing director Shannon Wells said in a statement.
"At this time, our thoughts are with the families of the persons on board."
There has been increased air traffic in recent days around the Tasman Peninsula to monitor the progress of race yachts as they make their final turn toward the Hobart finish line.
