A group of people at a west London immigration removal centre caused “disturbance” on Saturday morning, the Home Office has claimed.
No one was injured during the incident at Harmondsworth detention centre near Heathrow Airport, but the power was still out just before 9am on Saturday, the department said.
The Home Office initially claimed that a “group of detainees left their rooms” and went into a courtyard area “armed with various weaponry”, but later withdrew that claim.
Police, fire and HM Prison services are at the scene.
A Home Office spokesperson added: “There has been a power outage at Harmondsworth immigration removal centre, and work is currently underway to resolve this issue.
“We are aware of a disturbance at the centre and the appropriate authorities have been notified and are on scene.
“The welfare and safety of staff and individuals detained at Harmondsworth is our key priority.”