It comes as a car belonging to William’s now-deceased foster grandmother at the time he went missing was also seized from a home at Gymea, in Sydney’s south, under a coronial order last Tuesday.
The vehicle, a grey Mazda hatchback, is undergoing forensic analysis, which is expected to take several weeks.
The car has changed ownership since the woman died in March.
“This activity relates to inquiries and search operations currently being conducted in the Kendall area,” NSW Police said in a statement.
William, at the time aged three, disappeared from the foster grandmother’s property on Benaroon Drive in Kendall at about 10.30am on September 12, 2014.
Overnight, NSW Police sifted through the garden below the second-storey balcony at the home.
Detectives are investigating whether the toddler fell from the balcony and used luminol – a chemical to detect the presence of blood – and a cadaver dog during the search.
Australian Federal Police officers will also join the investigation today, bringing ground-penetrating technology and X-ray devices in their search for William’s remains.
Hundreds of police officers and dozens of Rural Fire Service volunteers descended on Kendall on Monday to undertake new searches of the area where the boy went missing.
NSW Police Deputy Commissioner Mal Lanyon said this morning the investigation is ongoing and so he would not be able to comment on specifics.
“What I can say is the investigation is part of the dogged determination of investigators who will leave no stone unturned to do that,” he said.
When asked about the case, NSW Premier Dominic Perrottet said: “police are doing a phenomenal job”.
“I think I can speak on behalf of everyone across the state who have been heartbroken by this entire story that we have a breakthrough as soon as possible,” Mr Perrottet added.
Yesterday morning, NSW Police Commissioner Mick Fuller told 2GB: “I’m confident that the team who has the investigation at the moment can solve it.”
When asked whether detectives were focusing on anyone of interest, Mr Fuller added: “My understanding is, from the investigators, is that there is certainly one person in particular that we are looking closely at.”
Announcing the new operation on Monday, police confirmed they were looking for William’s remains.
Aside from the house, police are also examining a bushland site about one kilometre away, clearing the scrub yesterday.
WILLIAM TYRRELL’S DISAPPEARANCE: WHAT WE KNOW
- William Tyrrell vanished from his foster grandmother’s house in Kendall, NSW, on September 12, 2014
- His foster mother is being treated as a person of interest in his disappearance
- Police are investigating whether William fell from a second-storey balcony at the Kendall home
- Detectives used a substance to detect blood and a cadaver dog to scour a garden at the property
- Another search is underway in bushland about 1km from the Kendall property
- Detectives have confirmed they are looking for William’s remains
- A grey Mazda previously owned by the now-deceased foster grandmother has been seized