A former nurse who is in prison for the killing of a toddler in 1982 has been charged with murder over the death of an infant a year earlier, and authorities said 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 prison in Gatesville, Texas, for the 1982 killing of 15-month-old Chelsea McClellan and an incident involving a four-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 had been due to be freed next March under a mandatory release law that was in place when she was convicted, but Bexar County district attorney's office has announced she has been charged over 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's 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 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 is not clear why Jones's actions, involving so many suspected victims, were not detected earlier, but Sam Millsap, a previous district attorney in Bexar County, said in 2013 that medical records at the San Antonio hospital at one point were accidentally destroyed, hampering efforts by investigators.
Chelsea died after receiving an injection at a clinic in Kerrville, north west of San Antonio, and prosecutors at Jones's 1984 murder trial said the nurse lethally injected children there to demonstrate the need for a paediatric intensive care unit at a nearby hospital.
Other prosecutors theorised that Jones's tactic was to take swift medical action and save some of her victims, making herself appear to be a sort of miracle worker.
Mr LaHood said the new murder charge is based on fresh evidence that came to light and a review of old evidence. He also said the deaths of some of the other children are being re-examined and that additional charges could be coming.
Jones has been consistently denied parole over the years. She was due to be released next March after serving a third of her sentence under a mandatory release law adopted in 1977 to help alleviate prison overcrowding.
The law was overhauled 10 years later.
Jones, whose case has been chronicled in two books, a TV movie and numerous articles, was "emotional" when she was served an arrest warrant on Thursday, Mr LaHood said.
"We have every reason to believe that she fully expected to get out next year," he said.
Because of the new charge, Jones will be transferred to Bexar County jail while the case is prosecuted. A murder conviction brings a maximum sentence of 99 years.
Mr LaHood said Jones is not eligible for the death penalty because Texas did not have such a sentence at the time of the 1981 death.
"We will do our best to ensure that Genene Jones takes her very last breath behind bars," he said.