Illegal immigrants have injured five officers during a riot at a detention centre, according to border officials.
Up to 40 detainees were involved in the incident at Morton Hall immigration removal centre in Swinderby, Lincolnshire, which saw one detainee taken to hospital and led to 12 others being transferred to other centres.
A UK Border Agency (UKBA) spokesman said on Wednesday: "All our Immigration Removal Centres are overseen by an Independent Monitoring Board.
"Morton Hall is a safe place for detainees and staff. We will not tolerate any behaviour which might put anyone at risk of harm."
Staff were injured on 30 December, the UKBA said, while up to 50 detainees were also involved in a protest on Christmas Day, in which no-one was injured.
Both incidents were brought under control within an hour.
Morton Hall, a former women's prison, was reopened as an immigration removal centre in 2011 after a £6 million refit. It holds up to 392 foreign national offenders, failed asylum seekers and illegal immigrants.
The UKBA's website states that inmates at the all-male centre have access to 24-hour medical services, a dentist, a "well-stocked" library with "a wide array of reading material in different languages as well as DVDs and CDs".
There are also indoor badminton, soft tennis, volleyball and basketball courts.
In September last year, 18 asylum seekers went on hunger strike at Morton Hall because they did not want to be sent back to Afghanistan.