North Queensland police say they are still hopeful of finding a 22-year-old man missing for five days in "rugged" bushland.
Four specialist police units and seven remote trackers have joined the search for Ben Chisholm, who was last seen five days ago at Nelly Bay on Magnetic Island.
Police and emergency services launched drone and helicopter searches over the weekend to scour dense bushland.
The search has so far recovered the missing man's hat and shirt but police said they had no working theories about what happened to the 22-year-old.
Police also confirmed they had been in touch with Mr Chisholm's family before his disappearance following reports of unusual behaviour.
In 'rugged terrain'
Acting Inspector Mark Camilleri said the arrival of specialist police and remote trackers would help emergency services better scour the "very, very rugged" terrain and abseil into unreachable areas.
"The tree cover and tree canopy is fairly thick. That's why we've got a specialist helicopter to hover low, and the drones.
"But at this point in time, it's fairly hard going."
Queensland police, the State Emergency Service, Rural Fire Service, and Parks and Wildlife Service have been focusing their search around the Nelly Bay area in the south-east, following reports Mr Chisholm was seen heading towards Arcadia walking tracks.
Acting Inspector Camilleri said they would consider expanding the search to the sea.
"As the search progresses, we'll move onto that stage if we need to," he said.
"Hopefully we won't."
Mr Chisholm was last seen on Wednesday wearing shorts and a dark overcoat.
Police are urging anyone with information or possible sightings to come forward.
