STOCKHOLM — A single-engine plane crashed on a small island in northern Sweden, killing all nine people onboard, eight of them members of a parachute club.

The plane took off from a regional airport near the university city of Umea at 1:30 p.m. on Sunday and crashed on a tiny island in a river not far away, according to Malin Axroth, a police spokeswoman. She said the first report of a crash came in at 2:10 p.m.

Hans Ytterberg, director general of the National Board of Accident Investigation, said on Monday that he could not speculate about the cause of the disaster, but that the plane was not whole when it plunged to the ground about 300 miles north of Stockholm.

“Based on the films that we have seen and the wreckage pieces that we have looked at, we can conclude that parts of the plane had broken off in the air,” he said at a news conference.