A desperate search for missing RAF gunner Corrie McKeague was today extended for another three weeks.

The 23-year-old vanished after a night out with his friends in Bury St Edmunds, Suffolk, on September 24 last year.

His mother has now vowed to hire a private investigator if police fail to find her son who has been missing for more than seven months.

Nicola Urquhart, 47, spoke of her grief on ITV's Good Morning Britain and fears someone has lied to police.

Suffolk Police are continuing to search for missing gunner Corrie McKeague at the Milton landfill site near Cambridge

Officers are still at the site and continue to search in the hunt which was originally estimated to take up to 10 weeks

Nicola Urquhart, 47, told of her grief eight months after her 23-year-old RAF gunner son went missing after a night out with friends in Bury St Edmunds, Suffolk

She added that she had heard some 'ridiculous' theories about her son's disappearance.

And hours after her appearance on the show, Suffolk Police revealed that they will continue their search on the landfill site at Milton in Cambridgeshire.

More than 3,500 tonnes of waste has been searched but no trace of the young airman has been found.

The hunt, originally estimated to take up to 10 weeks, is now in its 11th week.

Ms Urquhart told the show: 'I've always tried to say that unless Corrie's physically found, I'm not going to let my own head go to the police that he may be dead.

'But I think it's completely unrealistic now to think anything other than that. So all I can do is just keep trying to find him.

'There are loads of theories out there and some of them are ridiculous, but this is ridiculous. He's walked into a dead end - he's not come back out again on camera.

'Only four vehicles go in there. He's left in one of those vehicles, so either somebody's not telling the truth or he's ended up at the landfill.'

Police have spent thousands of hours and £1million looking for Mr McKeague, who was at first thought to have tried walking back to his base at RAF Honington.

Volunteers have also taken part in searches organised by his family, but no evidence of his whereabouts has been found.

Ms Urquhart told ITV's Good Morning Britain presenters Piers Morgan and Susanna Reid that she fears someone has lied to police and that she had heard some 'ridiculous' theories

Police have spent thousands of hours and £1million looking for Mr McKeague (pictured), who was at first thought to have tried walking back to his base at RAF Honington

A search team is pictured combing through a landfill site in Milton, near Cambridge, in March

A Suffolk Police spokesman said on Wednesday: 'The search has been expanded after waste linked to both the right dates and the right location were found outside the initial cell area identified.

'As this type of search is so unusual, it was not known how the waste would have moved and as the work has progressed officers have gained a greater understanding of both how the waste is deposited and spread out, and the nature and construction of the site.

'Officers continue to take all of this into account as the search continues.

Mr McKeague is pictured with his girlfriend April Oliver, 21, who is expecting his child

'The work is under constant review and now, in week 11, in view of the dates on items still being found and advice from officers on the ground and the site team, it is likely the search will continue for at least three further weeks to ensure that the area holding waste from the relevant period is comprehensively examined.'

Ms Urquhart added: 'The search that they've been carrying out, they have found things as small as mobile phones - it really is a thorough search. I have no doubt from the way that the police have described it to me that if Corrie were there they would have found him.

'So it's not the case that they'll get to the end of this search of this cell and say 'he might still be in there'. I don't believe that. If they don't find him in there, it's because he's not in that cell.'

More recently, police officers have been combing through a landfill site in Milton, near Cambridge.

A bin lorry collected rubbish in an area behind some shops where Mr McKeague was last seen on CCTV.

It is now thought he may have crawled into a commercial bin for shelter and was accidentally crushed before the load was taken to the tip.

His mobile phone signal followed the route of the lorry on the night. The evidence was initially dismissed because the refuse firm wrongly recorded the weight of the load it picked up as 11kg.

Ms Urquhart retraced Mr McKeague's steps on the night he went missing in September

A bin lorry collected rubbish behind some shops where Mr McKeague was last seen on CCTV

It was later corrected to more than 100kg. Two months into the search at Milton, however, no trace of him has been found.

Speaking to presenters Susanna Reid and DailyMail.com U.S. Editor-at-Large Piers Morgan, Ms Urquhart said: 'I can't even begin to describe what it's like.

'I know millions of people go missing every year, and my son's no different to anybody else that goes missing, but the circumstances surrounding Corrie's disappearance are just so bizarre. I suppose that's just what keeps me going.'

She continued: 'I think exactly as the police have been saying to me, just now we still have the rest of this week, I could get a phone call this week saying that they've found him.

'As the DI said to me, if they keep finding rubbish that is that date, that place, then they will keep looking in those areas.

Last week, Mr McKeague's girlfriend April Oliver (pictured) shared a poignant black and white first image of her baby bump as she prepares to give birth to his child

Mr McKeague was last seen on CCTV walking on a street in Bury St Edmunds in the early hours

'It's not time constraints that are stopping it – it's where the search will naturally end. But if there is only one other cell right beside it, and Corrie's not found, I think the police would just naturally start to search that – it wouldn't be a case of me trying to urge them to do anything.'

Last week, Mr McKeague's girlfriend April Oliver shared a poignant black and white first image of her baby bump as she prepares to give birth to his child.

Clutched in her left hand was a tiny pair of boots similar to the Timberlands Mr McKeague was wearing when he was last seen in September.

April Oliver posted the photo on Facebook, where she wrote: 'I miss and love Corrie with every part of my body and little things set off different emotions.

'I can't help but be truly unconditionally in love with my baby and you're not here yet.

Ms Urquhart is pictured during the search for her missing 23-year-old son last December

Ms Urquhart joins search and rescue volunteers near his base at RAF Honnington in Suffolk

'You bring so much pain yet just as much joy and your daddy would be proud of you my little one and would love you as much as I do.

'Corrie will be a part of both of us forever and no one can take that away.'

A Suffolk Police spokesman said last week: 'Throughout the search officers have found material that have indicated they are in the right area – finding waste that was clearly identifiable as being from Bury St Edmunds and within the right time frame.

'The work being completed is continually being reviewed, with daily updates being passed to senior officers overseeing the investigation.

'In view of the dates on items still being found and advice from officers on the ground and the site team, the search will continue.'