Brule County state's attorney Theresa Maule Rossow also confirmed the number of casualties and praised the "heroic" actions of authorities who responded to the crash amid ice, heavy snow and gusting winds. Among the dead were the pilot and two children, Sioux Fall's KELO-TV reported.
Knudson said nine people were killed and three were injured.
Three survivors managed to escape the wreckage and were taken to nearby hospitals.
The plane had embarked shortly before noon from Chamberlain, South Dakota, and crashed about a mile southwest of there, according to the Federal Aviation Administration. The Weather Service warned of ice, snow and winds gusts asstormy weather around the USA is predicted to hit millions of travellers returning from Thanksgiving trips.
The FAA said investigators were en route to the crash site and that the National Transportation Safety Board (NTSB) would be in charge of the investigation.
The Pilatus PC-12 aircraft had an intended destination of Idaho Falls Regional Airport, Lunsford said. The cause of the crash has not been determined.
CHAMBERLAIN, S.D. - A single-engine plane crashed near Chamberlain Saturday. The airplane was registered to Conrad and Bischoff Inc. of Idaho Falls, according to FAA records.