The Metropolitan Police were called to Colnbrook Immigration Removal Centre in Colnbrook Bypass at around 9.15am on Thursday, December 1after the victim was assaulted.
He was taken to a west London hospital but he died there at around 9.30pm.
Formal identification has not yet taken place and the Met says a post-mortem examination will take place “in due course.”
Three men were arrested on suspicion of attempted murder after the assault – aged 31, 32, and 35.
The 32-year-old man remains in custody at a west London police station while the other two men were released with no further action.
Detectives from Homicide and Major Crime Command, led by Detective Chief Inspector Mark Lawson are investigating.
The Met says no one else is being sought in connection with the investigation.
Colnbrook opened in 2004 and according to campaign group Detention Action has a capacity of 408.
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