Day 10: search for hiker intensifies as more help sent

Dozens of extra specialist search operators have been deployed to help find a bushwalker missing in dense and challenging terrain for 10 days.

Experienced hiker Hadi Nazari, 23, was last seen on Boxing Day descending the challenging Hannels Spur trail in NSW's Kosciuszko National Park.

"There have now been more than 300 people searching across the nine days, all highly-skilled and trained," Riverina Police District Acting Superintendent Jill Gibson said on Saturday.

"Our focus and efforts continue to be finding Hadi and returning him to his family."

The operation has intensified, with six Rescue and Bomb Disposal Unit specialist police officers winched into the dense bushland by aircraft to access remote areas more quickly.

Six specially trained volunteers will camp overnight to further extend the search.

The large-scale search involving NSW Police, the State Emergency Service, National Parks and Wildlife Service, NSW Ambulance, and volunteers was launched when Mr Nazari failed to meet friends at Geehi campground.

Rubbish and hiking poles believed to belong to Mr Nazari were found near the Kosciuszko River late on Tuesday, narrowing the search area in the challenging terrain of the Hannels Spur Trail.

Experienced bushwalking guide Doug Chatten said the area was unforgiving, particularly for anyone who ventured off track.

"If you're off the track, it's bloody tough country," Mr Chatten told AAP.

"It's no easy walk, that's for sure ? you'd be a hard person to find."

The Hannels Spur trail, with its 1800m elevation change, is one of Australia's most difficult bushwalking routes.

Temperatures have risen, creating hot and humid conditions that further complicate the operation.

Aircraft from the Rural Fire Service, Westpac Surf Life Saving, and national parks are aiding in the extensive multi-agency search.

Ms Gibson said rugged terrain and dense vegetation made the search challenging.

"The bushland is so dense that searchers in some parts can't see their feet," she told reporters on Friday.