FORT WORTH — The estranged wife of an internationally known pianist pleaded not guilty Wednesday to charges that she killed the couple’s young daughters at their Texas home.

Sofya Tsygankova entered her plea during a brief court appearance in Fort Worth. Her arraignment came one day after she was charged in the deaths of 5-year-old Nika Kholodenko and 1-year-old Michela Kholodenko.

Vadym Kholodenko, a winner of the prestigious Van Cliburn International Piano Competition, discovered his daughters’ bodies March 17 when he arrived at the home to take them to school. Arrest affidavits say the girls were found dead on beds.

A pillow partially covered the head of the youngest child, but police Commander David Babcock said Wednesday that investigators haven’t determined whether the children had been smothered. He said that determination would be made by the Tarrant County medical examiner’s office.

Records for the office indicated that the children died of ‘‘homicidal violence’’ and that autopsies are pending.

Tsygankova was kneeling on the floor wearing a blood-stained nightgown and ‘‘rocking back and forth,’’ the affidavits say.

Associated Press