Two children and two adults on a "family joy ride" have been killed after a plane crash northeast of Brisbane.
Queensland Police said a 67-year-old man from Wamuran was the pilot of the light airplane which came down near Scarborough about 9am on Sunday after taking off from nearby Redcliffe Aerodrome where his family were waiting.
A 41-year-old Brisbane man, his 10-year-old daughter and nine-year-old son also died in the crash.
Inspector Craig White said the pilot's family at the aerodrome became aware of the crash after they began looking at social media when the single-engine, four-seater plane failed to return.
"There are a number of family of the pilot who were at the Redcliffe Aerodrome at the time of the accident," he said.
"I understand it was a bit of a family day ... a family joy ride.
"The family became aware when they knew the aircraft hadn't returned on site, also they began looking at social media posts."
Media reports suggest the plane - a Rockwell Commander 114 light airplane - may have flipped after engine trouble prompted the pilot to attempt to return to the landing strip.
"This is a tragic accident. It's leading up to Christmas and this is the last thing that any family needs to go through at this time of year, or any time," Insp White said.
"The (pilot's) family are deeply traumatised as you would expect."
A multi-agency operation is underway with water police and divers along with the force's forensic crash unit assisting other agencies including the Australian Transport Safety Bureau.
ATSB Chief Commissioner Angus Mitchell said early reports are that the plane crashed not long after take-off.
He said a Brisbane ATSB team were on site to help recover the plane from "quite inaccessible" mangroves off Scarborough, with Canberra investigators set to arrive on Monday.
He said a preliminary report on the crash's cause would be available in six to eight weeks.
Anyone who witnessed the crash or with information have been asked to contact police or the ATSB.
