Independent investigators are examining whether there were failings over a death that sparked unrest at an immigration removal centre.
Rubel Ahmed, thought to be in his 20s and originally from Bangladesh, died at Morton Hall in Lincolnshire on Friday.
Mr Ahmed's cause of death is not yet known, but is thought to have been either natural causes or suicide.
The Home Office would not say why Mr Ahmed had been detained, but said such deaths were "rare but tragic".
A cousin of Mr Ahmed told the Guardian he was "incredibly shy, quiet and reserved", and his family did not believe Mr Ahmed would have taken his own life.
A fellow detainee said Mr Ahmed had complained of chest pains and had been banging and kicking the door asking for help shortly before his death.
Lincolnshire Police said it was not investigating Mr Ahmed's death.
'Help prevent similar deaths'
Instead, it will be investigated by the Prisons and Probation Ombudsman (PPO).
A PPO spokeswoman said: "Our independent investigation will aim to identify the full circumstances of the death and whether there were any failings in Rubel Ahmed's care.
"Where possible we will identify lessons to be learned and make recommendations to the Home Office to help prevent similar deaths in future."
The Home Office has not detailed the nature of the "disturbance" following Mr Ahmed's death.
However, a detainee said they had got together outside of their units as they wanted to talk directly to the Home Office and the media.
"They are being very wrong to us inside and they are treating us like criminals and murderers," said the detainee.