A 40-year-old man died in New York City jail custody Tuesday morning after he was found unresponsive at Rikers Island, less than 24 hours after a 41-year-old woman died at the women’s jail on the same complex.

Umais Khan was found unresponsive in his bed by another person in custody shortly before 11 a.m., according to the Department of Correction.

Staff performed CPR until medical workers arrived, but Khan could not be revived and was pronounced dead. The cause of death has not been determined.

His death came less than a day after Rajpattie Ramkellawan, 41, died at the Rose M. Singer Center on Monday morning and brings the number of people who have died in or shortly after leaving city jail custody this year to at least four.

Mayor Zohran Mamdani has pledged to improve conditions at Rikers and eventually close the jail complex. The back-to-back deaths come as federal monitors continue to cite the department for failures in supervision, emergency response and medical care.

"I am absolutely devastated that we have lost someone in our care and this tragedy is felt by every member of service," Correction Commissioner Stanley Richards said in a statement.

Mamdani said Tuesday that he was “devastated to learn of the death of a person in city custody this morning” and that the department and its oversight partners had begun investigating.

"Our administration remains firmly committed to the urgent and essential work of creating better conditions in our city's jail system and closing Rikers Island as quickly as possible," he said.

On Monday, the mayor called Ramkellawan’s death a “heartbreaking tragedy.”

Court records show Khan had a history of theft-related arrests. He was most recently arrested on May 5, a day after prosecutors said he pried open the front door of a Manhattan residence near MacDougal and Prince streets and stole a package.

He was remanded without bail after missing earlier court appearances, records show. Khan’s attorney did not return a phone call seeking comment.

In a statement, City Councilmember Selvena Brooks-Powers, who chairs the committee on criminal justice issues, said the deaths were "alarming and unacceptable."

"While we wait for further information, I’m calling for a swift, thorough investigation to understand what happened and how to prevent future deaths," the councilmember said. "It is my hope that these findings can better inform the work of the Remediation Manager. Rikers should not be a death sentence; we must end this cycle."

'She's a beautiful soul'

More details also emerged Tuesday about Ramkellawan, who died Monday after what the department described as a medical emergency.

Her sister, Nadira Jaman, said Ramkellawan moved to New York from Guyana more than two decades ago and had struggled with addiction.

“My sister, obviously, she’s a beautiful soul,” Jaman said. “She went through some stuff. Drugs got a hold of her and she was suffering from that.”

Jaman added, "Her last moments were not with her family, and she wasn’t even a bad criminal."

Katherine LeGeros Bajuk, a mental health attorney specialist with New York County Defender Services, which represented both Khan and Ramkellawan, said Ramkellawan had endured “unimaginable trauma and adversity.”

New York County Defender Services Executive Director Stan Germán issued a statement Tuesday night saying the group was "eagerly" awaiting the results of the medical examiner's autopsies.

"Rikers Island is not a treatment center for those struggling with mental illness and addiction," Germán said. "Our city must do better."

The deaths follow those of Barry Cozart, 39, at the George R. Vierno Center on March 25 and John Price, 49, who died days later after being transferred from Rikers to Elmhurst Hospital.

At least 15 people died in or shortly after leaving city jail custody last year, according to department records.

This story has been updated with comments from City Councilmember Selvena Brooks-Powers and New York County Defender Services Executive Director Stan Germán.