The city's Correction Department is investigating after a second person in under a week dies while in its custody.
Officials say the detainee passed away Sunday.
NY1 was told the man had health issues and was transported from Rikers to Bellevue hospital, where he died.
This comes just a few days after a transgender woman died while being detained on Rikers.
Layleen Polanco was found dead in her cell Friday at the Rose Singer Center for women.
Her death prompted outrage and protests from activists.
"I would like to extend my deepest condolences to both of their families and loved ones during this difficult time. We take such matters extremely seriously, and investigations into both incidents are ongoing," said Cynthia Brann, the Commissioner of the DOC.
The Correction Department says it doesn't suspect foul play in either death.