A 31-year-old woman incarcerated at Rikers Island died Wednesday, officials said. She was the 21st person to die in city custody since the beginning of last year.

The cause of Mary Yehudah’s death is under investigation, according to the Department of Correction. She was pronounced dead at Elmhurst Hospital. The Daily News reported that Yehudah suffered a drug overdose.

Yehudah was in custody at the Rose M. Singer Center on Rikers. She was held since February on a robbery charge.

“Ms. Yehuda’s passing fills us with sadness, every life here is precious. Our thoughts are with her family and loved ones,” said Department of Commissioner Louis Molina in a statement.

Yehuda is the fifth person to die while incarcerated at Rikers this year. Three of those deaths occurred after correction officers failed to render aid, according to a report from an independent oversight body, the Board of Correction. Part of the problem, the report said, was there weren’t enough officers available in the housing units who were authorized to interact with inmates.

Staffing problems continue to plague Rikers. Thousands of correctional staff can be out sick on any given day.

To that end, attorneys for detainees are asking the federal government to intervene and take over Rikers Island. City correction plans have devised an action plan, now before a judge, which they hope will resolve staffing shortages at the facility.