Search teams have spent the past 26 days scouring the bush for any signs of the missing three-year-old who disappeared from his late foster grandmother's home on Benaroon Drive seven years ago.

One of the main focus areas of the renewed search is a patch of bushland on the corner of Cobb and Co Rd, just one kilometre from where William was last seen in 2014.

This search site has now expanded to the opposite side of Batar Creek Rd, with NSW RFS volunteers assisting police in clearing dense bushland. Markers have also been placed to section off the areas to be searched.

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A stretch of bushland along Batar Creek Rd and Benaroon Drive has also been cleared this week.

A faded red piece of fabric was found in the muddy creek bed on Monday (December 6) and has been sent away to be forensically examined.

The search team has found a number of pieces of material during the search which have all been sent away for testing. It is not yet known whether any of the pieces of material are related to the case.

Geomorphologist Jon Olley told the Daily Telegraph that bones of a child would likely break down in the soil that is currently being searched.

"The one thing we have going in our favour is the fact that (investigators) believe he was in a polyester suit. That doesn't break down and it's very resistant to actually fading as well," he said.

"There possibly would be bones, but given the level of bioactivity here, and the amount of humic acids that are in the soils, that would actually help break them down over time."