WELD COUNTY — Authorities are conducting an investigation after a small airplane went down in a field in Weld County.

According to the Federal Aviation Administration, the single-engine Cessna 120 crashed under unknown circumstances sometime before 3:30 p.m. Saturday, just west of Platte Valley Airpark outside Fort Lupton.

The Weld County Sheriff's Office says the two people on board the plane survived and had already taken themselves to the hospital before deputies got to the scene. The cause of the crash is unknown.

The FAA and the National Transportation Safety Board are investigating the crash.