Nine people have been taken to hospital after suffering smoke inhalation during a disturbance at Campsfield House immigration detention centre, in Kidlington.
'Tornado' teams of prison officers equipped to deal with riots were sent to the scene.
A Home Office spokesman said the incident began at 6.30am.
Seven immigration staff at the centre, which is run by private company GEO UK, and two detainees had been taken to hospital, she said.
"Police, fire and ambulance teams are on the scene and a number of Tornado units from the Prison Service have been deployed to the centre," the spokesman said.
Fire and ambulance crews were called at about 7am following reports of a blaze in a detainee's room.
About 25 firefighters tackled the flames, which are thought to have spread to neighbouring rooms.
Police cordoned off the entrance to the centre and workers were prevented from getting on to the site.
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