A Nigerian man whose death in a detention centre in the United Kingdom is the subject of an investigation by the Home Office repeatedly said he was feeling unwell in the weeks leading up to his death.Oscar Okwurime died last week at the Harmondsworth removal centre, where he was found by another detainee.According to family members, Okwurime, 34, repeatedly told authorities he was ill but didn't receive medical attention."I told him straight away: 'tell the authorities there and they will get you checked'," Okwurime's brother, identified only as Alex, told The Independent newspaper."That first week they didn't do anything. And the second week, he said they were still saying nothing. The last time I saw him, he told me he was on a waiting list of about 400. He said he was feeling pain in his side." 201442371424250913 Alex, who said his brother didn't have any health issues before his detainment, called Oscar's death "a pure case of negligence"."If someone is in your custody and telling you they're not feeling well, it's your duty of care to get them checked," he said.The family's story was corroborated by two people who knew Okwurime from the Hammondsworth facility.According to one, the Nigerian asked staff repeatedly for a doctor but was told "this was not a quick process" at the facility.The other said Okwurime tried to get an appointment with a nurse.Okwurime had been in detention for about three weeks after entering the United Kingdom on a visitor's visa and subsequently asking for asylum.Following his death, the high court stopped the removal of three people who could shed light on the circumstances under which Okwurime died.The UK has been criticised regularly for its system of indefinite detention for those seeking asylum.Migrants from countries where safe return is not guaranteed or those with disputed nationality can be held for years.The government has defended the practice, saying putting constraints on the time people can be held would severely limit its immigration policies.