Four people were killed in a small plane crash in western Wisconsin, officials said Monday. The crash occurred about 5:15 p.m. in Polk County, near the Minnesota border.

Authorities found a single-engine Beech M35, a six-passenger aircraft, in flames in a rural field. The Polk County Sheriff’s Office said, in a statement, that bodies of the four passengers were found inside after firefighters doused the fire, the Associated Press reported. All of the deceased were reportedly from Wisconsin but officials did not provide the names or ages of the deceased.

The Midwest Medical Examiner's Office in Anoka, Minnesota, will perform autopsies and identify the victims, according to Duluth News Tribune newspaper.

Witnesses told CBS affiliate WCCO that they saw the plane twirl down and crash before being engulfed in flames. They reportedly rushed to the site and tried to help those onboard.

Authorities reportedly said that the plane might have taken off about 50 miles from the crash site. The Federal Aviation Administration and the National Transportation Safety Board are investigating the crash.