Oregon police say the woman accused of throwing her two children into the Willamette River has a history of domestic violence and recently filed for separation from the children's father.

Authorities say Amanda Jo Stott-Smith will be arraigned Tuesday on aggravated murder charges in the death of her four-year-old son, and aggravated attempted murder in the case of her seven-year-old daughter who survived a fall of 75 feet and is said to be improving.

Portland police say it's a miracle the girl survived after being in cold water for more than a half-hour.

Stott-Smith was taken into custody in Portland some six hours after her children's screams were first heard on the river.

Police say she had threatened to jump off a ledge when officers arrived.

They have not released a motive.