WATFORD CITY, N.D. (AP) - The National Weather Service says the tornado that touched down at an oil patch worker camp was an EF-2.
Preliminary information suggests the winds reached 120 mph.
The weather service says a second brief tornado possibly occurred in the area based on eyewitness accounts.
The twister touched down about 7:50 p.m. Monday at a worker camp with 15 trailers just south of Watford City, about 50 miles southeast of Williston.
A 15-year-old girl, who was from out of state and visiting an aunt and uncle, was critically injured and is in intensive care at a Minot hospital. Eight other people were treated at a Watford City hospital for lesser injuries.
The American Red Cross says eight residents spent the night at a shelter and that several families were among those displaced.