Two men are in hospital following a fire at an immigration detention centre, the Home Office said.
Ten fire engines were called to the Campsfield House immigration removal centre in Kidlington, near Oxford, at 9pm last night.
A Home Office spokesman said: "A fire at Campsfield immigration removal centre has led to more than half of the detainees being relocated to other removal centres around the UK.
"All the detainees have been accounted for and two male detainees are now in hospital. The cause of the fire is being investigated by police and the fire service."
The UK Border Agency website says the centre, privately run by MITIE, has space for 216 beds.
It describes Campsfield House as a long-term centre for men, who are detained pending the outcome of their immigration case and subsequent removal.
The fire broke out in one of the three blocks that make up the centre.
The immigration centre forms part of a larger site used for training purposes for the prison and police services.
People living nearby described seeing the emergency services arriving and a strong smell of smoke.
A woman, who declined to be named, said she and her husband heard sirens and looked out of their front door towards a side entrance into the compound to see "four or five fire engines at about 9pm, coming down the road".
"I could smell smoke but it was hazy and damp last night so it was difficult to see anything over there," she said.
Another couple, who have lived near to the centre for four years, said it was "quiet" and there had been no trouble in the time they had been there.
Their neighbour, a woman who has lived in the road more than 30 years, said she smelled what she thought was "bonfire smoke", later hearing sirens.
She said there had been very little trouble over the years. "We had some escapees a few years ago, maybe six years ago, but they caught them.
"They caught one of them in a back garden in a house up the road, but we've had no trouble at all since."
Throughout the morning minibuses with blacked-out windows have been coming and going at the site.
A team of fire investigators from Oxfordshire Fire and Rescue Service arrived at the centre at about 11.20am, as experts piece together the cause of the blaze.