FILE - In this Feb. 16, 1984, file photo, Genene Jones, second right, is escorted into Williamson County Courthouse in Georgetown, Texas. Jones, a former nurse who's been serving a 99-year prison sentence since 1984 for the fatal overdose of an infant in her care, is due for early release in March 2018. A grand jury indicted her on Thursday, May 25, 2017, in the death of another infant as prosecutors try to keep her behind bars. (AP Photo/Ted Powers, File)
FILE - In this Feb. 16, 1984, file photo, Genene Jones, second right, is escorted into Williamson County Courthouse in Georgetown, Texas. Jones, a former nurse who's been serving a 99-year prison sentence since 1984 for the fatal overdose of an infant in her care, is due for early release in March 2018. A grand jury indicted her on Thursday, May 25, 2017, in the death of another infant as prosecutors try to keep her behind bars. (AP Photo/Ted Powers, File) Credit: Ted Powers

A Texas nurse who is in prison for the 1982 killing of a toddler has been charged with murder in the 1981 death of an infant, and authorities said Friday that they think she may have killed up to 60 young children around that time.

Genene Jones, 66, has been serving concurrent sentences at a prison in Gatesville for two 1984 convictions: a 99-year prison sentence for murder in the death of 15-month-old Chelsea McClelland, who was given a fatal injection of a muscle relaxant, and a 60-year term for injury to a child for giving 4-week-old Rolando Santos a large injection of the blood-thinner Heparin.

On Thursday, the Bexar County district attorney’s office announced that a grand jury had returned a murder indictment against Jones in the 1981 death of 11-month-old Joshua Sawyer, who investigators say died of a fatal overdose of an anti-seizure drug.

During Jones’ time working in hospitals and clinics in San Antonio and elsewhere in Texas, children died of unexplained seizures and other complications.