Yoselyn Ortega, 50, was arrested earlier this month and charged with the murders of Lucia Krim, 6, and her brother Leo, 2.
Court documents released Tuesday show the grand jury indicted Ortega on first- and second-degree murder charges in both deaths.
Police say on October 25, the children's mother, Marina Krim, returned to the family's Upper West Side apartment, found Lucia and Leo dead in the bathroom and saw the nanny stab herself with a kitchen knife.
Ortega has been recovering since then at Weill Cornell Medical Center under police watch, and was still there as of Tuesday, according to hospital spokeswoman Linda Kamateh.
Krim left two of her children with the nanny to take her 3-year-old child, Nessie, to a swim lesson at a nearby YMCA, New York Police Commissioner Ray Kelly said last month. She had expected to meet the nanny around 5:30 p.m. at a dance class, but when Ortega failed to appear she went back to the apartment.
The late children's father is Kevin Krim, a senior vice president for CNBC Digital and former Yahoo executive.
A native of the Dominican Republic, Ortega had been a naturalized U.S. citizen for 10 years.
Image: Courtroom, via Shutterstock