RALEIGH (AP) — Advocacy groups have asked federal authorities to investigate solitary confinement in North Carolina prisons, citing the death of a mentally ill prisoner and separate concerns by President Barack Obama.

The request comes weeks after the state agreed to pay a $2.5 million settlement to the family of the prisoner, who died after being held in solitary confinement for 35 days. Earlier in July, Obama separately announced a federal review of how the practice is used in prisons.

Groups including the American Civil Liberties Union and North Carolina Prisoner Legal Services sent the letter on Monday asking for a Justice Department investigation.

“Understaffed, underfunded, and plagued by arbitrary standards, insufficient oversight, and inadequate resources for inmates with mental illness, North Carolina’s solitary confinement regime must change,” the letter states. “However, governmental efforts and calls from the media and the public have resulted in little meaningful reform.”

The letter cites the treatment of mentally ill inmates and tells several of their stories. The letter says prisoners can be isolated for minor infractions such as profanity or misbehavior that results from mental illness. For at least 23 hours a day, the isolated prisoners have no sunlight, fresh air or human contact, the letter says.

Featured prominently is the story of Michael Anthony Kerr, whose 2014 death led to the financial settlement as well as several firings and resignations at Alexander Correctional Institution in Taylorsville.

Records show the 54-year-old inmate was twice cited for violations by prison staff for flooding his cell weeks before his death. Kerr was found unresponsive in the back of a prison van after being driven three hours to a mental hospital at Raleigh’s Central Prison.

An autopsy determined Kerr died of dehydration on March 12, 2014, and was receiving no treatment for his schizophrenia.

The N.C. Department of Public Safety website listed Kerr as a habitual felon serving a 31-year sentence after he was convicted of firing into a house in October 2008.

The Justice Department’s media relations staff didn’t immediately respond to an email seeking comment.