Police were drafted in to support staff at an immigration detention centre when trouble flared overnight.
Disturbances broke out overnight in all four wings of a controversial immigration detention centre.
A Home Office spokesman said staff at the Harmondsworth complex, near Heathrow airport in west London, were in negotiations with detainees.
Police and prison staff from across southern England were called to assist at the Harmondsworth complex, near Heathrow airport, west London.
The perimeter of the site has been secured, said the spokesman.
Staff are now in discussions with detainees and the perimeter has been secured, said the Home Office.
The Metropolitan Police said they were called at about 0040GMT and officers were providing assistance. Fire crews are also on standby.
A prisons' watchdog report heavily criticised the centre's regime this week after repeated disturbances.
This week a report the centre was criticised for repeated disturbances .
Bullying fears
Chief inspector of prisons Anne Owers said Harmondsworth in west London was hard to run - but her report was the poorest ever on a removal centre.
The Metropolitan Police said they were called at about 0040GMT and officers were providing assistance at the scene. Fire crews are also on standby.
In the report published on Tuesday, chief inspector of prisons Anne Owers said the complex was hard to run - but her report was the poorest ever on a removal centre.
Detainees said they feared bullying, and staff were unaware of a special plan to prevent suicides.
Detainees said they feared bullying, and staff were unaware of a special plan to prevent suicides.
The Home Office said it would draw up a plan to improve the centre.
The Home Office said it would draw up a plan to improve the centre.
The centre near Heathrow Airport is the largest in the country, handling thousands of people facing deportation every year. In 2004 a detainee committed suicide, sparking a major disturbance that led to its temporary closure.
The centre near Heathrow Airport is the largest in the country, handling thousands of people facing deportation every year.
In 2004 a detainee committed suicide, sparking a major disturbance that led to its temporary closure.
Since then, Harmondsworth has been at the centre of ongoing campaigns against detention of failed asylum seekers.
Since then, Harmondsworth has been at the centre of ongoing campaigns against detention of failed asylum seekers.
In 2005, some 50 Zimbabweans held at the centre launched a hunger strike to try to force their cases back into the courts, saying they had been unfairly treated.
In their July inspection, inspectors found:
More than 60% of detainees felt unsafe
Almost half (44%) said they had been victimised by staff
Detainees described custody officers as aggressive, intimidating and unhelpful
The report also criticised the management's over-emphasis on physical security and their strict control of all movements. These measures went as far as banning detainees from keeping nail clippers.
At the same time, actions to prevent self-harm and suicide were weak, despite the commitment of one co-ordinator.
An "action plan" designed to minimise suicide attempts, drawn up after an earlier incident, had not been shared with the centre's suicide prevention team. "It was purely a bureaucratic exercise which had had no impact" concluded the inspectors.
Junior staff had limited access to the centre's ligature cutters, equipment needed to stop suicidal detainees from hanging themselves.
However, inspectors did find some areas of good practice including good interaction between senior officers and detainees, the value placed on education and chaplaincy staff by detainees and some good healthcare provision.
'Humanity and dignity'
But Anne Owers said: "This is undoubtedly the poorest report we have issued on an Immigration Removal Centre.
"Harmondsworth is not an easy place to run, and the serious disturbance it had experienced had clearly affected the confidence of managers and staff.
"However, it had been allowed to slip into a culture and approach which was wholly at odds with its stated purpose, and inimical to the proper care and treatment of detainees."
Liam Byrne, Home Office minister, said he welcomed the report and took its recommendations "very seriously".
"Detention is an essential part of an effective immigration system, but it is critical that it is done with humanity and dignity."
He said the Home Office was drawing up an action plan.
