An evening of horseback riding ended in tragedy Sunday night near Frenchtown, when a 30 year-old woman was killed after being thrown from her horse.

Jeremiah Peterson with the Missoula County Sheriff's Office said a party of four were riding near Frenchtown in western Montana when the accident occurred.

Peterson said it was unknown what caused the horse to throw the woman. He said the Frenchtown Rural Fire Department and Missoula Ambulance Services responded to the scene. The woman was taken to St. Patrick Hospital where she was declared dead.

No names have been released pending notification of next of kin. Peterson said the investigation into the incident is still underway.