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."
More top news
Ms Leadsom has received the backing of Ian Duncan Smith, the former work and pensions secretary.
"This was mindless vandalism at its very worst, which has wrecked a much-loved community facility."
Three people have been taken to hospital after a taxi collided with pedestrians and a lamppost this afternoon.