The Swedish defense ministry says a soldier hurt when a passenger train collided with an armored vehicle in southern Sweden has serious but not life-threatening injuries.

In a statement, the military said Wednesday that those injured in the collision Tuesday were a woman and two men, all Swedes aged 25, 26 and 30. The train driver also was slightly injured.

It said the accident near Trosa, south of Stockholm, was being probed by police and by Sweden's Accident Investigation Authority. The cause of the accident was not known.

The military said the armored vehicle was part of the country's largest military exercise in more than 20 years, involving nearly 20,000 Swedish and foreign troops. It said, despite extensive preparations for military exercises, "there is always the risk of accidents."