The UK Border Agency has confirmed the demonstrator on the roof of the Morton Hall centre in Swinderby near Lincoln is a detainee of the immigration centre.
"There is currently a peaceful protest ongoing at Morton Hall in which one detainee has scaled the roof.
"We are working with the Prison Service to resolve the situation."
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Some showers, although many places will stay dry.
Mainly dry tonight. Showery rain spreading in tomorrow.
Team GB swimmer Adam Peaty, from Uttoxeter in Staffordshire, has broken the world record for the 50m breast stroke.