Earlier Thursday, AMSA said that, of the two objects spotted, the large one was about 24 metres long.
"The objects are relatively indistinct. The indication to me is of objects that are of a reasonable size and probably awash with water and bobbing up and down on the surface," Xinhua quoted Australian Maritime Safety Authority (AMSA) official John Young as saying at a press conference in Canberra.
"The largest... was assessed as being 24 metres. There is another one that is smaller than that," he added.
A Royal Australian Air Force (RAAF) Orion aircraft arrived in the area about 1.50 p.m.
A further three aircraft have been tasked by RCC Australia to the area later in the day, including a Royal New Zealand Air Force Orion and a US Navy P8 Poseidon aircraft.
The Poseidon aircraft is expected to arrive at 3 p.m. The second RAAF Orion is expected to depart RAAF Base Pearce at 6 p.m. The New Zealand Orion is due to depart at 8 p.m.
An RAAF C-130 Hercules aircraft has been tasked by RCC Australia to drop datum marker buoys.
These marker buoys assist RCC Australia by providing information about water movement to assist in drift modelling. They will provide an ongoing reference point if the task of relocating the objects becomes protracted.
A merchant ship that responded to a shipping broadcast issued by RCC Australia Monday is expected to arrive in the area about 6 p.m.
Meanwhile, the HMAS Success is en route to the scene. The ship is equipped to recover any objects that have been located.
