The Sarpy County Sheriff's office says speed and alcohol were factors in the tragic crash that killed four Gretna High School classmates June 17.
Sheriff Jeffery Davis said Abigail Barth's blood-alcohol level was 0.09% when the 2017 Ford Fusion she was driving left the road near 180th Street and Platteview Road shortly after 11 that night.
The legal limit to drive in the state is 0.08%.
Davis said the investigation revealed Barth had been driving more than 90 mph in the 55 mph zone when her car struck the end of a guardrail and ended up in a ravine near a creek just west of 180th Street.
The car was in flames when deputies arrived.
Alexandria Minardi, 15, and 16-year-olds Barth, Kloe Odermatt and Addisyn Pfeifer died at the scene.
The lone survivor, Roan Brandon, 15, was released from a Lincoln hospital earlier this month.
Davis said all but Pfeifer had alcohol in their system.
He said investigators looked into preliminary reports that they had been at a party in the area, but they haven't found any evidence to support it.