The driver of a car seen near the campsite where a young girl went missing last weekend is being sought by West Australian police, who stress they are a not a suspect in the disappearance.

Detectives want to talk to the driver of the vehicle spotted two hours after missing four-year-old Cleo Smith was last seen in her family’s tent, as well as anyone who was camping nearby.

Police believe Cleo was taken from the tent at the Blowholes site on WA’s north-west coast in the early hours of last Saturday morning.

Detective Superintendent Rod Wilde on Sunday afternoon said a car was seen turning south off Blowholes Road between 3am and 3.30am that morning.

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“We want the person or persons who were in that vehicle to come forward and contact police,” Mr Wilde said.

“We want to know who they were and what they were doing.”

Mr Wilde stressed the driver was not a suspect.

Cleo was last seen by her parents about 1.30am last Saturday. Her mother Ellie Smith said she woke at 6am to discover she was missing.

It has been confirmed the zipper on the tent was found open to a height Cleo could not have reached, seemingly ruling out the possibility she wandered off on her own.

Her red and black sleeping bag is also missing.

Mr Wilde said the witnesses who spotted the car were “credible sources”.

He also called on anyone camping within the vicinity last weekend to call police.

“There’s still people out there that we want to catch up with and to speak to,” Mr Wilde said.

The WA government on Thursday issued a $1 million reward for information about Cleo’s whereabouts.

Premier Mark McGowan said every resource had been directed into finding Cleo and he urged anyone with information to come forward.

“We all feel for her and her family and we just want to make sure that we find her as soon as we can, and that every, every effort is made to uncover her location so that the family can find out where she is,” Mr McGowan said on Sunday.

At the same press conference, Commissioner Chris Dawson said police would “painstakingly go through every vehicle movement” and every piece of forensic evidence.

“This is a large-scale investigation, but it is in a remote locality,” Mr Dawson said.

“So in one sense, we’ve got an opportunity here to put a very large footprint around whoever was in the area at the time, it’s that sort of level of investigation and effort that we are capturing now.”

He said there was no information to suggest Cleo was not still in Western Australia.

-AAP