South Carolina authorities say a mother who claimed her children drowned when their car careened into a river has been charged with murder after confessing to suffocating the toddlers and then faking the accident.

Sheriff Larry Williams said Tuesday that 29-year-old Shaquan Duley told police she was distraught after a dispute with her own mother and killed her children by putting her hand over their mouths.

He said Duley then strapped the children into her car and drove it into a river in Orangeburg County, located about 70 kilometres southeast of Columbia, the state capital. Duley is to be arraigned Wednesday.

Duley was originally arrested Monday and held on a charge of leaving the scene of an accident after her two sons were found dead in a vehicle in the North Edisto River.

Autopsies were planned Tuesday on the bodies of two-year-old Devean C. Duley and 18-month-old Ja'van T. Duley to determine how they died.