THE mother of missing RAF airman Corrie McKeague has said she is trying to stay upbeat despite growing fears that police may have been searching the wrong area of a landfill tip for his remains.

Nicola Urquhart's comments came as the bill for the total search to find Mr McKeague, missing for eight months, hit £1 million.

Specialist teams of police officers have spent the past two months sifting through 3,000 tonnes of rubbish at the site in Cambridgeshire, almost 30 miles from where the Scot vanished on a night out in September last year.

Police have now started winding down the search of a large segment - or 'cell' - of the site previously thought most likely to contain Mr McKeague's remains.

It is believed he was transported there by a bin lorry after falling into a skip in Bury St Edmunds, Suffolk.

The search is likely to change tack and switch to the fringes and entrance to the vast area.

Asked if she was prepared for the possibility her son's body may never be found, Ms Urquhart, 48, said: “There is no way that we can prepare ourselves for that.

"My main focus from the outset has been to find Corrie and so we must remain positive and carry on.

“The main 'cell' has been searched and nothing found. The search will now concentrate on the edges and the entrance in under where the excavator’s have been.

Ms Urquhart, a liaison officer with Police Scotland, added: "I genuinely believe that Corrie is within that landfill, my only fear is that there has been a mistake and we have been searching in the wrong area.”

Mr McKeague, 23, from Dunfermline, Fife, was last seen on CCTV entering a bin loading bay in the centre of Bury St Edmunds in the early hours of September 24.

The link to the landfill site came about records showed that a bin lorry that was in the area at the time weighed far more than it should have, indicating that it could have been accounted for by a body.

Police have so far spent nine weeks searching the landfill site for any sign of the gunner who is stationed with RAF Honington, in Bury St Edmunds.

Ms Urquhart, 48, said her son's girlfriend, April Oliver, who announced in January that she was pregnant with Mr McKeague's child, is 'doing well.' Ms Oliver found out about the pregnancy after he disappeared.

She said: “She still has a while to go and both her and the baby are doing well. She just doesn’t want any attention just now, her concern is still finding Corrie.”

The search is one of the most costly carried out by Suffolk Police.

A force spokesman confirmed that officers had been through all the material deposited in the area from the location and time he disappeared.

He added: "However, towards the edges of the area it has also been noticed that the waste may have naturally shifted from the original deposition area.

"Police are expanding the search parameters to take this into account."

On the total costs so far of the operation, a spokesman added: "With an estimation of staffing costs, including salaries, overtime and specialist resources included in the total, over £1 million has been spent on the investigation to date."

“The total spent on the investigation above and beyond staffing costs is currently around £544,250.”

Last month officers said they had started to find rubbish at the site “from the right time period” from when he went missing.

Mr McKeague's father, Martin, 48, from Cupar, said he made made 10 visits to the site, with the latest this week the hardest yet.

Speaking this week, he praised the efforts of teams. “That’s probably because we’re getting so close to having searched the part of the cell – the area in the landfill where we believe my son ended up," he added.