COPENHAGEN, Denmark (AP) -- Swedish accident investigators on Friday said the country's oldest amusement park didn't properly test new parts for a roller coaster that derailed last year and sent some passengers plunging to the ground, killing one and injuring nine others, one seriously.

The June 25 derailment at the Grona Lund park in Stockholm "was caused by deficiencies in the ordering, manufacturing and testing of new support arms for the Jetline trains," the Swedish Accident Investigation Authority said. It said the support arms weren't sufficiently strong.

The roller coaster was carrying 11 passengers at the time of the derailment. The front of the train jumped off the tracks, leaving one car tilted toward the ground. A woman in her 30s was thrown out of the ride and died. Two others also fell from the train, one of whom was seriously injured and the other received minor injuries. Seven other passengers also had minor injuries.

Grona Lund park CEO Jan Eriksson said at a news conference that "out of respect for the accident and everyone involved, we have decided to close Jetline for good."

"Something like this has never happened before at Grona Lund and we will make sure that something like this will never happen again," Eriksson said, according to Swedish news agency TT.

Police have also launched a separate criminal investigation into the derailment. Christer B. Jarlås, a prosecutor for the National Unit for Environmental and Work Environment, said police have carried out extensive interrogations, technical examinations of the train carriages and material analyses. He said there is currently no timetable for when a decision will be made on whether to charge anyone.

The 800-meter-long (half-mile-long) roller coaster opened in 1988 and was renovated in 2000, according to Grona Lund. It has a maximum height of 30 meters (98 feet) and a top speed of 90 kph (56 mph).

Grona Lund opened in 1883.