"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."

Three police officers could be seen standing guard outside the site on Saturday, while a police van with more officers inside was parked in the grounds.

An unmarked black Mercedes-Benz fire service vehicle entered the detention centre around 10:30am, closely followed by another two unmarked cars a few minutes later. 

All three vehicles had their blue lights flashing. Shortly after two London Fire Brigade fire engines arrived at the site. 

Around 11:30am, a white bus left the site with 30 men on board, many of them waving at onlookers from behind the tinted windows.

TSG officers deploy 24-hours a day to high-risk incidents including public order offences, spontaneous disorder, and large-scale public events.

Migrants moved from the centre will not be moved into hotels

Colbrook, also known as Harmondsworth, holds around more than 670 adult males who are awaiting deportation after having an asylum claim denied or still awaiting a decision but are considered at risk of absconding. 

The Telegraph understands that the migrants moved from the centre will not be moved into hotels, and they will not be immediately bailed or released when they do not have proof of a fixed address.

Colnbrook, which is run by Mitie, can hold up to 676 adult males, making it the largest detention centre in Europe.

A spokesman for Mitie said: “The Harmondsworth site of Heathrow immigration removal centre lost electrical power because of an outage in the local area.

“We are working closely with the Home Office to ensure the safety of those in our care while work is carried out on site to resolve the issue.”