Four immigrants were on the run today after escaping from a detention camp via a network of pipes.

The Vietnamese men broke out of the Oakington Immigration Centre in Longstanton, Cambridgeshire.

Sources said the group cut through razor wire fences after crawling through a metal service duct similar to those used for air conditioning.

A spokesman for the UK Border and Immigration Agency said: "We are currently working to recapture four detainees.

"This is an ongoing operation so we cannot comment further.

"We believe that these men do not pose a threat to the public."

The spokesman said the men, who escaped the overnight lock-up between Thursday and Friday, were being detained for possessing cannabis and forged documents.

The centre, a former RAF base, can hold up to 352 men and opened in 2000.