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Three more men are said to have ecaped on Sunday
Seven immigrants have gone on the run after escaping from a detention camp in Longstanton, Cambridgeshire.
Four Vietnamese men broke out of the Oakington Immigration Centre on Thursday and Friday.
They are believed to have cut through razor wire fences after crawling through a metal service duct.
The Home Office later admitted three others had escaped from the centre some time on Sunday, but refused to give any details about the men or their escape.
The UK Border Agency said it was "determined to recapture" the detainees.
A spokesman said: "This is an ongoing operation so we cannot comment further. We believe that these men do not pose a threat to the public."
The Vietnamese men, who escaped the overnight lock-up between Thursday and Friday last week, were being detained on suspicion of possessing cannabis and forged documents.
The centre, a former RAF base, can hold up to 352 men and opened in 2000.