DALLAS — A Texas nurse who is in prison for the 1982 killing of a toddler has been charged with murder in the death of an infant a year earlier, and authorities said Friday that they think she may have killed up to 60 young children around that time.Genene Jones, 66, is serving concurrent 99-year and 60-year sentences at a Gatesville prison for the 1982 killing of 15-month-old Chelsea McClelland and the sickening of a 4-week-old boy who survived. The girl was given a fatal injection of a muscle relaxant and the boy received a large injection of a blood thinner.Jones was due to be freed next March under a mandatory release law that was in place when she was convicted. But on Thursday, the Bexar County district attorney's office announced that she has been charged in the 1981 death of 11-month-old Joshua Sawyer, who investigators say died of a fatal overdose of an anti-seizure drug, Dilantin.During Jones' time working in hospitals and clinics in San Antonio and elsewhere in Texas, children died of unexplained seizures and other complications.At a news conference Friday in San Antonio, District Attorney Nico LaHood said investigators believe Jones may have killed some or all of those children because they died under unusual circumstances during or shortly after her shifts."She's been suspected in dozens of infant deaths and she's only been held accountable in one," he said.It's not clear why Jones' actions, involving so many suspected victims, were not detected earlier.