The three-year-old hasn’t been seen since he vanished from his grandmother’s home at Kendall on Friday morning.
But authorities and members of the Kendall community aren’t giving up their search.
Teams have again worked through the night and police say all avenues to find the boy in his Spider-Man costume are being investigated.
However they admit hopes are fading that it’s still a rescue mission.
‘Those chances of survival diminish rapidly and of course we are very concerned for young William’s welfare,’ Superintendent Paul Fehon told reporters on Tuesday.
‘We do have grave concerns.
‘To disappear that quickly absolutely bewilders us.’
The search will be expanded today from 1.5km around the home, which backs onto bush, out to three kilometres, with police on trial bikes venturing further afield.
‘The whole operation has covered in excess of 10 square kilometres,’ Supt Fehon said.
Police are looking at all possibilities.
‘Our investigative efforts, we are bolstering them to ensure if anything has happened to William apart from him running and disappearing of his own means that we come up with the right result,’ Supt Fehon said.
‘We would have hoped to have found something by now.’
He said investigators were “keeping an open mind” about whether the boy had been taken.
Police in the mid-north coast area have been working with specialist units across the state, including the sex crime squad.
It’s been reported that known sex offenders in the area have been contacted to confirm their whereabouts at 10.30am last Friday, the ABC says.
A family friend of the Tyrells has described William as a happy three-year-old.
‘William is a gorgeous little boy, happy cheeky adventurer,’ she told the Seven Network.
Fresh search crews from Sydney and Newcastle are arriving today.
Police will hold a briefing on Tuesday morning to discuss the plan for the day.