Specialist drones have been deployed to look for a missing runner as police warn volunteers not to join the search.
Jenny Hall, 23, was last seen leaving her home in Barracks Farm, County Durham, in her car just after 3pm on Tuesday.
Durham Constabulary said her last known location was on the B6278 between Stanhope and Eggleston - where her red Ford Focus was parked.
As the major search operation entered its fourth day on Saturday, police said officers - along with search and mountain rescue teams - will be working in Hamsterley Forest and the surrounding areas to look for any trace of her.
Specialist drones have also been brought in as the latest tool in the search.
"We want to thank the public for their ongoing support and whilst we appreciate the offer of volunteers, we would ask that people do not join the search themselves as this could disturb the ongoing work and potentially distract expert sniffer dogs," police said in a statement.
Chief Inspector Dean Haythornthwaite said families out in the forest should "allow those officers the space to carry out their search and try not to disrupt that search area".
Ms Hall is described as white and 6ft tall with dark brown hair.
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She was last seen wearing a blue hoodie with a John Deere logo and dark jogging bottoms.
Her family told police she may have been carrying a green jacket and had her hair up in a ponytail.
On Friday, officers said they were becoming "increasingly concerned" as the search concentrated on running trails between Eggleston and Hamsterley used regularly by Ms Hall.
More than 100 miles of track have been searched in the Teesdale area by officers, the rural community and local landowners.
Digital intelligence officers have also carried out extensive inquiries into Ms Hall's mobile phone, smart watch and running apps, but the force said "none have yielded any results unfortunately".
Anyone who believes they may have seen Ms Hall or has any relevant information about her whereabouts is asked to contact police.
(c) Sky News 2025: Jenny Hall: Don't join in search for missing runner, 23, police tell public - as drones deploye
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