A seaplane crashed into a Sydney river yesterday, killing six people on a "wine and dine" sightseeing flight ahead of the city's harbour-centred New Year's Eve celebrations.
Four Britons were feared dead in the crash.
New South Wales Police Force said divers had recovered six bodies from the scene and an investigation was under way to identify the victims and determine the cause of the crash.
Six people including the pilot were on board the plane when it crashed off Jerusalem Bay near Cowan, north of Sydney, at around 3.10pm (4.10am Irish time) yesterday, police said.
Police said they did not immediately know the cause of the crash, nor the identities of the five passengers, but were speaking with several witnesses who were in boats on one of the waterways' busiest days of the year. The pilot was the sixth victim.
The aircraft was operated by Sydney Seaplanes, a major tourism operator in the city. Several visiting celebrities have flown on the company's sightseeing planes, including pop stars Ed Sheeran and Sam Smith, tech mogul Bill Gates, comedian Jerry Seinfeld and actor Cuba Gooding Jnr.
Police said the seaplane was returning the party of five people from a waterside restaurant in Sydney's north to the Sydney Seaplanes headquarters in Rose Bay in the city's east when it crashed into the water, immediately sinking.
"We have spoken to a number of witnesses," Acting Superintendent Michael Gorman told reporters, adding that forensic police would inspect the plane to assess when it could be raised from the seabed.
"It's too early in the investigation so we don't know why the plane crashed."
Mr Gorman said police were liaising with Sydney Seaplanes to identify the victims and their families would be contacted before they were named publicly.
Sydney Seaplanes has been operating since 1938, originally flying from Australia to Britain, a journey that required 30 refuelling stops along what became famous as the "Kangaroo" route.
Local reports said four Britons were among the dead.
The UK foreign office was unable to confirm any details of the crash, but said British officials are in contact with authorities in Sydney.
A spokeswoman said: "Officials from the British consulate are in contact with local authorities. We stand ready to provide consular assistance."
New South Wales Police Force and the Australian Transport Safety Bureau (ATSB) are investigating the cause.
The ATSB said the single-engine plane operated by Sydney Seaplanes is reported to have "sunk rapidly" after hitting the water.
"At around 3pm this afternoon, a DHC-2 Beaver Seaplane, VH-NOO, operated by Sydney Seaplanes was flying in the vicinity of Jerusalem Bay (near Cottage Point)," the bureau said.
"It is understood that there was one pilot and five passengers on the aircraft on a return flight to Rose Bay.
"The sequence of events leading up to the accident are not yet understood, however following the impact with the water, the aircraft is reported to have sunk rapidly."