Eleven passengers and a pilot who appear to have been taking off for a skydiving trip in Missouri were killed in a plane crash on Sunday near the Butler Memorial Airport, the Missouri Highway Patrol said.

Emergency responders received a call about the plane crash at about 11:30 a.m. local time. All of the occupants were found dead near a field adjacent to the airport, said Sgt. Justin Ewing of the Missouri Highway Patrol.

Sgt. Ewing said that investigators do not know what caused the crash but added that it was unlikely to have been related to the weather.

The Butler Missouri Police Department and the Bates County Sheriff’s Office were also on the scene, he said. The Federal Aviation Administration and the National Transportation Safety Board have also been contacted.

The Butler Memorial Airport is a small airport that is used by some skydiving companies, Sgt. Ewing said. Local authorities do not have information about the plane or how the occupants died.

This is a developing story and will be updated.