A plane that fatally crashed into the Swan River during an Australia Day event will remain in the water until the Australian Transport and Safety Bureau inspects it today.
The pilot and passenger died when the Grumman G-73 "Mallard" flying boat broke up on impact af 5pm on Thursday in front of horrified families celebrating Australia Day at the Perth Skyshow on the river foreshore.
"The plane seemed to be banking and then it looked like it was turning too sharply and just seemed to fall into the water," witness Mark Annette Stuart said.
It's believed the plane was part of an airshow over the Swan River ahead of the City of Perth's annual fireworks display.
Radio 6PR reported on Friday morning the plane had recently been bought in the United States and that one of the deceased passengers could possibly be its owner.
The seaplane remained in situ and guarded by water police but could be removed on Friday pending a decision by the Department of Transport and inspection by the Australian Transport Safety Bureau.
The tragedy was captured on video and posted to social media by several witnesses.
A huge bang and plume of water could be seen as the plane hit the surface nose first.
Up to 10 pleasure craft nearby on the river sped to the scene near Heirisson Island and tried in vain to rescue the occupants, a male and a female.
WA Police acting commissioner Stephen Brown said the cause of the crash was "unknown".
"For reasons yet unknown, it's entered the waterway, thankfully without injuring anyone else on the ground or any other people who are here at the event," he said.
The fireworks were cancelled out of respect for the dead and to "conserve the integrity of the site", the City of Perth said in a statement.
More than 300,000 people had been expected to attend the Skyworks show around the river but were sent home just hours before its scheduled start after the incident.
WA Police will provide an update on the incident later on Friday.
- with AAP