Three people remain hospitalized as federal agencies investigate the cause of the helicopter crash that injured them, according to the Douglas County Sheriff’s Office.

About 2 a.m. Saturday, a North Memorial Medical Center helicopter went down on the east side of Lake Winona en route to the airport in Alexandria, Minn.

On board were pilot Joshua Jones, 47, flight nurse Scott Scepaniak, 44, and flight paramedic Miles Weske, 34. All three are hospitalized at North Memorial Medical Center in Robbinsdale, according to the sheriff’s office. There were no patients on board.

Officials from the Federal Aviation Administration and the National Transportation Safety Board arrived Saturday to investigate. Officials hope to remove the wreckage by Monday and transfer it to Minneapolis, where it will remain throughout the investigation, the sheriff’s office said.