A roller coaster accident at the oldest amusement park in Sweden killed one person and injured nine others when the train partially derailed on Sunday.

Several passengers riding the Jetline roller coaster at Gröna Lund park were sent plunging to the ground when the front of the train flew off the track for unknown reasons, park officials said.

The train cars stopped between 20 and 25 feet above ground, though witnesses said two or three people fell out, one of whom managed to cling to the track.

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The passenger who died has not been publicly identified. Most of the injured, including three children, were released by Monday. Four adults remained hospitalized, two of them in serious but not life-threatening condition, the regional government said.

The Swedish Accident Investigation Authority on Monday launched a probe into how the roller coaster train partially derailed. Separately, police have launched a criminal investigation on possible charges of involuntary manslaughter, causing bodily harm and danger to others.

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Officials estimate that the park will remain closed for at least one week.

Located on an island near Stockholm's city center, Gröna Lund opened in 1883 and is one of Sweden's most popular amusement parks. The 2,600-foot long Jetline roller coaster opened in 1988 and was renovated in 2000, according to the park. It has a maximum height of 98 feet and a top speed of 56 mph.

The Associated Press contributed to this report.