Police are looking at the disappearance of missing girl Charlise Mutten in the NSW Blue Mountains as a possible homicide, as the search for the nine-year-old continues.

Divers have today searched the Hawkesbury River at Windsor, after seizing a boat from the Mount Wilson estate where her Family said she was last seen.

Charlise has been missing for four days, after her family said she disappeared on Thursday.

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She was not reported missing to police until Friday morning and her mother has not yet been able to give an official statement.

The property she was staying at remains under police guard.

Rural fire service (RFS) volunteers have also discovered multiple sets of footprints on a trail, saying one seemed to be "very small and bare footed”.

"Certain items have been found and identified … but unfortunately haven’t led to anything that gives us a definite indication of her location," NSW Police Chief Inspector Gary Sims said.

Charlise, who lives with her grandmother in Queensland, was visiting her mother, Kallista, at fiancée Justin Stein's family property, which is a popular wedding venue.

Police divers, as well as more than 100 rescue volunteers have been deployed to the area in attempts to locate Charlise, as scorching summer conditions simmer around 30C.

"I think everyone I’ve met up here is just so, absolutely devastated. I mean the family, and the grandparents in particular, we’re just, keeping our fingers crossed that, that they find her," local resident Martin Barge said.

Officers have spent hours scouring murky ponds and surrounding waterways, while crews on dirt bikes ripped up fire trails in the frantic search, which has been made more difficult by the tough terrain, heavy undergrowth and steep descents.

Charlise was last seen wearing a pink top with a round neck collar, a black knee-length skirt and pink Nike thongs.

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Acting Superintendent John Nelson said officers were working closely with her family, including her mother, Kallista.

"For any parent it's a very distressing scenario so yeah she is quite distressed and we are providing her with support," he said.

Earlier, paramedics consoled Ms Mutten at the search centre while Mr Stein drove to Penrith to assist police with their enquiries.

A white boat has been seized from the estate and a car from a road nearby.

Anyone who has seen Charlise should contact Crime Stoppers.