A Jamaican man detained at Morton Hall immigration removal centre in Lincolnshire died in hospital on Tuesday of last week.
It was the third death in detention in Britain in just a month, following the deaths of a Polish man detained at Harmondsworth and a Chinese man at Dungavel.
Some 43 people have died in or shortly after detention since 2000.
The Prisons and Probation Ombudsman has launched an investigation into the Morton Hall death.
Evidence about the mistreatment of detainees, including at hospital or when suicidal, continues to stack up.
Thousands of refugees and migrants every year are locked up in detention centres.
There has been outrage whenever more evidence of abuse in detention centres has been brought to light.
The prison service, border agency, home office and private contractors must be made to answer for every life lost or abuse committed on their watch.
Hundreds of torture victims wrongly detained, rules judge
The government has wrongly locked up hundreds of torture victims in immigration detention centres, a judge ruled this week.
Mr Justice Ouseley made the ruling on Tuesday following a challenge by seven survivors of serious abuse. They included two men who had been tortured because of their sexuality.
A Home Office policy known as “Adults at Risk” was introduced in September 2016. It redefined torture to refer only to violence carried out by the state.
Ouseley said that this “narrowed definition” had allowed many torture victims to be wrongly imprisoned in Britain. He added that their experiences “may make them particularly vulnerable to harm in detention”.
One man, who had been tortured because of his sexuality in Nigeria, said being detained harmed his mental health. “In detention we are not regarded as human beings but as waste products,” he said.
This week’s judgement could lead to dozens more claims against the Home Office for unlawful detention.