Corrie Mckeague police investigation costs £2.1m to date
The police investigation into missing RAF airman Corrie Mckeague has cost £2.1m to date, according to figures.
Mr Mckeague vanished after a night out in Bury St Edmunds, Suffolk, in September 2016.
Information obtained by the BBC showed Suffolk Police has spent £1,325,000 on the investigation, plus £826,000 in officers' salaries.
The force said "careful consideration" was given to resourcing all major, long-running investigations.
Suffolk Police's budget for 2017/18 was £121.8m. The county's police and crime commissioner Tim Passmore has asked the government to cover the cost of the investigation.
According to data received by the BBC following a Freedom of Information request, officers have spent 34,000 hours on the investigation - not including police staff time or overtime.
The figures revealed 5,600 hours of overtime have been worked on the case, amounting to £235,000, excluding December's claims.
Suffolk Police Federation said the inquiry had brought "unique pressures" to the force.
Figures from the Home Office show there were 249,349 missing person reports across 42 police forces in England and Wales in 2015/16.
A study by the University of Portsmouth said the average cost of an investigation for a "medium risk, medium term missing person" was £2,415.
It said 70% of all missing person cases were "medium" and on average took 36 hours and 37 minutes of officers' time to investigate.
The Corrie Mckeague investigation has so far lasted one year and four months.
Report co-writer Dr Karen Shalev Greene said the Mckeague investigation was "one of the most expensive".
"But as an adult that went missing in as far as we know non-suspicious circumstances, I don't remember that intensity," she said.
Mr Mckeague, from Dunfermline, Fife, was last seen about about 03:35 BST in Bury St Edmunds, walking into a bin loading bay.
As part of the inquiry, police trawled a landfill site near Cambridge for Mr Mckeague's remains.
The landfill search has ended but the police investigation is continuing.
Darren Harris, chairman of Suffolk Police Federation, said the final eight weeks of the 28-week search were resourced by officers working on their rest days.
He said: "It's been unique, not only for Suffolk but for all police forces in England and Wales.
"Last time we have seen an investigation like this was in 2006 with the large-scale Steve Wright investigation with regards to the five working girls in Ipswich."