More police squads are heading to the NSW mid-north coast to step up the search for three-year-old William Tyrell, who hasn’t been seen since Friday.

Fresh crews from Sydney and Newcastle will arrive in the small town of Kendall on Monday.

Mounted police, dog teams, members of the SES, Rural Fire Service and local surf lifesaving club, and hundreds of volunteers spent all weekend searching for the little boy, who was last seen at his grandmother’s home on Friday morning.

• No sign of missing NSW boy as search continues

The search will concentrate on a 1.5km radius around the home, including dense scrub.

“We will continue to comb through very thoroughly that area close to where he was last seen,” Superintendent Paul Fehon told the Seven Network.

Police divers searched surrounding dams at the weekend for the boy, who was last seen wearing a Spider-Man costume.

Supt Fehon said police were “keeping an open mind” about whether he might have been taken.

“We are keeping an open mind in regards to anything as part of our search operation and our investigation,” he said.

“At this stage while there is hope for young William’s survival, we’ll search for him.”

The Tyrell family were distraught and wanted to thank all the volunteers for their help, Supt Fehon said.

Monday is a critical day because there is still a chance William is alive, he said.

“Everyone just wants to find the little boy,” he told AAP.

“A three-year-old child is full of adventure and we want to ensure we’re able to locate him safely.

“We want to concentrate on doing an extremely thorough search.”