A search for the remains of missing three-year-old William Tyrrell has entered its fifth day on the NSW mid-north coast, as rain threatens to hamper search efforts.

Police turned their attention to a nearby creek on Friday, pumping water from it ahead of showers and possible thunderstorms forecast for later in the day.

Shortly before midday, there was a flurry of activity among the searchers when officers found a small piece of cloth near the drained creekbed.

Media on the scene said investigators placed the cloth into an evidence bag before it was taken away.

A police spokesperson told watching journalists the cloth – which was light blue and measured about eight centimetres by eight centimetres – would be tested.

Police drained a creek as their search for William Tyrrell went into a fifth day. Photo: NSW Police

There was a similar discovery on Wednesday afternoon, when a clutch of red fibre was found by those digging in the area. It has also been sent for testing.

One senior NSW Police officer involved in the search was seen clutching a Spider-Man suit, similar to the one William was wearing when last seen. Police have been using it to compare to the scraps of thread that have been found.

Officers from Strike Force Rosann have spent the week searching the Kendall property where William was last seen in September 2014, as well as nearby bushland.

On Thursday, Australian Federal Police officers brought in ground-penetrating radar to scan a concrete slab at the Kendall house that belonged to the boy’s foster grandmother.

The slab was laid after the little boy disappeared.

Detective senior sergeant Mark Dukes holds a Spider-Man suit. Photo: AAP

Earlier, police investigated theories the boy might have been involved in a fatal fall from a balcony at the property.

Police have also seized a Mazda that previously belonged to the foster grandmother, who has since died.

Cadaver dogs have also been on the scene.

That day police also charged the boy’s former foster parents over an unrelated alleged assault on a different child.

The pair are due to face court at Hornsby on Tuesday

Prime Minister Scott Morrison praised investigating police officers on Thursday, saying they have made “huge inroads” and would “never stop” looking into the mysterious disappearance.

The findings of a coronial inquest into William’s disappearance, which concluded last year, are yet to be handed down.

A $1 million reward for information on the case still stands.

-with AAP