Police investigating the disappearance of RAF gunner Corrie McKeague have "explored all reasonable lines of inquiry", a review has found.
Suffolk Police said their search of a landfill site at Milton near Cambridge, which resumed on Monday, will continue and is anticipated to last four to six weeks.
A review of the force's investigation to date was conducted by the East Midlands Special Operations Unit and has now been completed, with a report passed to Suffolk Police.
A Suffolk Police spokesman said: "The report concludes that police have conducted a thorough, methodical and detailed investigation and explored all reasonable lines of inquiry with no new further leads needing to be pursued.
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"The review also concludes that Corrie is most likely to be in the Milton landfill site and the review also supports the continued search of the eastern end of cell 22 at the Milton landfill site which began on Monday."
Mr McKeague was 23 years old when he was last seen walking through Bury St Edmunds, Suffolk, after a night out with friends.
A five-month search of the landfill site was called off in July after no evidence of his body was found.
The latest search is focusing on an area next to the site of the earlier search.
Mr McKeague's mother, Nicola Urquhart, wrote on Friday that officers had found nothing in the first week of the resumed search.
"The search this week has been negative with no trace of Corrie or his belongings," she said.
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Mr McKeague, from Fife, Scotland, but based at RAF Honington in Suffolk, was last seen on CCTV at 3.25am on September 24 2016.
A bin lorry was caught on CCTV near Brentgovel Street in Bury St Edmunds around the time Mr McKeague was last seen.
It took a route which appeared to coincide with the movements of his phone.
The bin lorry linked to Mr McKeague's disappearance was initially thought to have collected a 24lb (11kg) load but police said it was later found to be more than 220lb (100kg).
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Mr McKeague's girlfriend, April Oliver, announced in June that the missing serviceman had become a father with the birth of their daughter.
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