An 18-year-old female passenger died Sunday night when her sister, allegedly driving under the influence, lost control of her car on Atlas Peak Road near Silverado Resort and Spa, the California Highway Patrol reported.

The CHP said the crash was first reported at 10:54 p.m. on Atlas Peak south of Hardman Avenue. Officers arrived to find one sister dead at the scene. The other was flown with major injuries to Kaiser Hospital in Vacaville.

The deceased was identified Monday afternoon by the Napa County Coroner's office as Michaella Margret Hanifan of Todd, North Carolina. 

The CHP said the driver, Finnuala Hanifan, 21, of San Francisco was driving a borrowed 2018 Porsche at a high rate of speed southbound when she lost control. Her car left the west edge of the roadway, crashed into an irrigation culvert, then continued south, striking two wooden poles and a traffic signal.

The car overturned and came to rest on the west shoulder of Atlas Peak Road, the CHP said.

The women were returning to nearby Silverado Resort and Spa, the CHP said.

The cause of the crash is under investigation, but CHP Sgt. William Bradshaw said Finnuala Hanifan is suspected of DUI. Both parties were wearing seatbelts and the car's airbags deployed, the CHP said.

According to the CHP, Pacific Gas and Electric shutdown power in the area to make the scene safe for first responders. PG&E's power outage website said 871 customers were without power as of 11:59 p.m. Sunday. 

By 11 a.m. Monday, all but 130 customers had their power restored. Everyone should be reconnected by 3 p.m., a PG&E spokesperson said.

Atlas Peak Road remained closed Monday morning between McKinley Road and Hardman Avenue, according to Napa County Public Works. 

This was the second motor vehicle fatality in Napa County over the weekend. On Saturday, a 71-year-old motorcylist died when two motorcycles collided head-on at Lake Berryessa. 

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Bay City News contributed to this story.