FORT WORTH, Texas -- A Texas medical examiner says the two young daughters of an internationally known pianist likely died of asphyxia.

The Fort Worth Star-Telegram reports that the Tarrant County medical examiner's office released the autopsy reports Thursday of 1-year-old Michela Kholodenko and 5-year-old Nika Kholodenko. Their mother, Sofya Tsygankova, has been charged in their deaths.

Vadym Kholodenko, a Ukrainian-born winner of the prestigious Van Cliburn International Piano Competition, discovered his daughters' bodies March 17 when he arrived at the Benbrook home the girls shared with their mother to take them to school. Arrest affidavits for Tsygankova, say the girls were found dead on beds.

The 31-year-old Tsygankova has pleaded not guilty to two counts of capital murder. She remains in the Tarrant County Jail with bail set at $2 million.