Police looking for missing nightclubber Sian O'Callaghan were "very close to identifying" her whereabouts, the detective leading the inquiry said today.
The announcement was made after the detailed search of dense woodland was narrowed following a breakthrough in mobile phone technology.
Specialist search teams were examining specific "hotspots" within the 4,500-acre Savernake Forest, near Marlborough, Wiltshire.
The use of mobile phone technology had pinpointed several areas of interest to the police and had allowed them to rule out large areas of the forest.
Around 400 members of the public, including friends and family of the missing office administrator, had joined police yesterday in the painstaking search of the woodland.
Today, police asked people to stay away from Savernake Forest - around 15 miles from where Miss O'Callaghan was last seen on Saturday - as the thorough search continued.
After a day's intensive examination of the thick undergrowth, Detective Superintendent Steve Fulcher, who is leading the inquiry, said: "We have made good progress in narrowing the search using a number of technologies and techniques and I believe we are getting very close to identifying Sian's whereabouts.
"Searches will be limited by available daylight but we will be further assisted by specialist dog teams who arrive tomorrow and resume the search effort as soon as daylight permits.
"Whilst I still want anyone with information to contact police I am not asking for any more public assistance with searches at this stage."
Earlier, Mr Fulcher said the inquiry was moving at a "rapid pace" with "significant lines of inquiry being developed".
He added: "The public have been fantastic in support of the search for Sian O'Callaghan and I'm very grateful.
"I've been able to use new technological techniques to provide a tighter search parameter and have been able to rule out large areas of the six-and-a-half-mile radius we have all been searching."
Police would not discuss the technological breakthrough but revealed earlier this week that phone masts put Miss O'Callaghan's mobile phone somewhere in the 4,500-acre forest just 34 minutes after she left Suju nightclub in Swindon at 2.52am on Saturday.
It was a journey that could only have been made by car, police said.
Miss O'Callaghan was caught on CCTV leaving the nightclub, in Swindon's Old Town area, after an evening out with girl friends.
The 22-year-old lived just half-a-mile away with her boyfriend Kevin Reape, 25, in a flat but she never made it home.
Police have spent days searching the forest's undergrowth and were inundated yesterday with help from members of the public.
Yesterday, an anonymous donor offered a £20,000 reward for information leading directly to Miss O'Callaghan being found.
Police have issued a new poster, with details of the reward, which is being pinned up across Wiltshire by volunteers and also warned people to be extra careful and not to be out walking alone.
The poster includes a picture of Miss O'Callaghan and CCTV footage of her leaving the club.
St Barnabas Church in Gorse Hill, Swindon, will open its doors at 7pm for a "Vigil Service And Prayer For The Safe Return Of Sian O'Callaghan", which was advertised on Facebook.