( CNN ) -- A 6-year-old boy was found dead in the frigid waters of Oregon 's Yaquina Bay after his mother told police she threw him off a bridge Monday evening , authorities said . The body of London McCabe was found in the water about a mile from the Yaquina Bay Bridge about 10:20 p.m. , roughly four hours after his mother called 911 to say she 'd thrown him from the span , Newport police said . The mother , Jillian Meredith McCabe , 34 , was arrested on charges of aggravated murder , murder and first-degree manslaughter , police said . McCabe , of nearby Seal Rock , called police around 6:30 p.m. Monday `` saying she threw her child over the side , '' Newport Police Chief Mark Miranda said . The water of Yaquina Bay is more than 100 feet below the bridge . Chances of survival from a fall that high were `` minimal , '' Miranda said . Even if a person survived the fall , the chief said , one could survive the frigid water for only about 20 minutes . Police have not commented on the cause of the boy 's death or a possible motive . McCabe was being held at the Lincoln County jail Tuesday morning with bail set at $ 750,000 . Two boats and a Coast Guard helicopter searched the water for hours before the body was found , Coast Guard spokesman Jonathan Klingenberg told CNN . CNN 's Greg Morrison and Tina Burnside contributed to this report .
NEW : The mother has been arrested on murder , manslaughter charges . NEW : Jillian McCabe , Tuesday , held with bail set at $ 750,000 . Yaquina Bay is more than 100 feet above the water . Woman told police she threw her son off the bridge , police say .