A mother pleaded not guilty Wednesday to aggravated murder and attempted murder after her two children plunged off a bridge into a frigid Oregon river.

An attorney entered the plea for Amanda Jo Stott-Smith, who appeared briefly in court in handcuffs. Her trial was set for July 15.

Stott-Smith, 31, was formally indicted on Tuesday. The aggravated murder charge means that she could face the death penalty.

Her 4-year-old son, Eldon Smith, died May 23 after falling into the Willamette River in Portland. His 7-year-old sister was rescued by residents who heard her moans in the darkness and jumped into their boat to investigate. She recovered and is now with her father.

Police have not said how they believe the children fell from the bridge.

Court records show Stott-Smith and her husband, Jason Smith, fought for custody of their children after he moved to Eugene. He was granted custody in April and Stott-Smith had visitation rights.

The state Department of Human Services plans to review its dealings with Stott-Smith.