Armed with rakes, hoes and a chainsaw, police started day one of what will be a four-week “forensic” search for William Tyrrell - the three-year-old who disappeared in 2014 while playing in his grandmother’s front yard on the NSW mid-north coast.

Fifty officers from the public order and riot squad will spend the month concentrated on three kilometres of scrubby, hilly bushland off Benaroon Drive in Kendall only a few hundred metres from where William was last seen.

The officer in charge of the investigation, the homicide squad's Detective Chief Inspector Gary Jubelin, said police had received 15,000 pieces of information since the then three-year-old disappeared on September 12, 2014.

But he would not say if any new information had led police to return to the Kendall township to carry out a new search.