Police to sweep roadsides for missing boy William Tyrell

Police will begin scouring the sides of roads on the NSW mid-north coast town of Kendall as the search for little William Tyrell enters its seventh day.

Police say they will look for discarded clues in their investigation into the disappearance of the three-year-old boy, who was last seen at his grandmother's house last Friday.

Police are trying to find a spot where William may have been "assisted" into a car.

Scores of police and volunteers have searched the regional town near Port Macquarie, including bushland and waterways, over the past six days.

Today teams of emergency services began the first of a two-day search of roadsides "in case something has been thrown", said NSW Police Rescue Sergeant John King.

"It will be a sweep search of the side of the road," he told volunteers at a briefing in Kendall on Thursday.

Police say the boy could not be alive after so long if he was in bushland, but they remain open-minded about what might have happened to him.

Sgt King told volunteers not to give up hope.

"We look at those statistics and this is a stand-alone case, so we still hold promise and we are going to continue with that attitude," Sgt King said.

A strike force has been set up to investigate the disappearance, including specialist police and officers from the sex crimes squad.