The area searched is about a 10-minute drive north of Kendall, where the three-year-old vanished while playing outside his foster grandmother's home almost six years ago.
Investigators are now focusing on an area near an old sawmill where convicted paedophile Frank Abbott lived in a caravan at the time of the toddler's disappearance.
SES volunteers and officers spent hours cutting through the thick bush around Walkers Creek next to an old train line.
A coronial inquest into the boy's suspected murder has previously heard the 79-year-old Abbott would often ramble to neighbours about the smell of a “dead human” near Herons Creek.
Shop owner Jan Anderson told the inquest that Abbott became obsessed with the Tyrrell case.
“He used to go on and on about a peculiar smell … We said it's probably a dead animal, a kangaroo.”
“He said, 'no, it's not that.' We said, 'why don't you go and tell the police?'
He said, 'I'm not going to do that … because if there's something up there, I'll get blamed for it.”
Abbott currently remains a person of interest linked to William's disappearance but has never been arrested or charged.
Photo credits: ABC
This article originally appeared on Over60.