CANTON - A woman under investigation in the decades-old deaths of her three children has been charged with killing a 2-year-old boy whose body was found last year in a bathtub at his home in St. Lawrence County.

Shirley Winters, 49, faces a charge of second-degree murder in connection with the death of Ryan Rivers at his grandparents' home in Pierrepont, according to her lawyer, Kenneth Moynihan.

She is also charged with first-degree assault and child endangerment, according to an indictment unsealed Tuesday.

Winters, who was visiting the home at the time of the death, pleaded not guilty at her arraignment and a judge set bail at $75,000 cash or $150,000 bond.

In June, an Onondaga County judge dismissed a murder indictment against Winters in the 1980 death of her 5-month-old son, ruling that the grand jury proceedings were tainted when prosecutors introduced evidence about the deaths of two of her other children in a Jefferson County house fire in 1979.

The Onondaga County district attorney plans to present the 1980 case to another grand jury.

The Rivers death prompted Onondaga and Jefferson county authorities to reopen investigations into the earlier deaths of the Winters children.