Police are draining a creek near Kendall on the NSW Mid North Coast as the search for William Tyrrell's remains continues for a fifth day.
It took several hours of using a Rural Fire Service pump to drain the creek, as investigators prepare to extend the search beyond the initial area.
Officers are also searching soil in the same pocket of bushland, running small sections through a motorised sieve.
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Several pieces of string have so far been found, with testing ongoing.
Australian Federal Police used ground-penetrating sonar over a concrete slab at the nearby home William disappeared from, but detected no anomalies.
The results of luminol testing to detect blood beneath the home's balcony are also underway, as detectives investigate the possibility that William fell from the balcony and was then transported into the bush.
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William was three when he disappeared from the Kendall home on September 12, 2014 and he has never been found.
The new searches were launched this week, with police confirming they were looking for William's remains.
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A car that formerly belonged to William's now-deceased foster grandmother was also seized and is undergoing forensic testing.
William's foster mother is being treated as a person of interest in the case.
She has not been arrested or charged.
