OITA – One man was killed and another was seriously injured over the weekend when they were hit by a roller coaster that was being tested at Kijima Kogen Park in Oita Prefecture, the police said.

According to the police, park employee Takashi Okubo, 44, and another employee were struck at around 3:30 p.m. Saturday while inspecting the tracks at the Jupiter, a wooden roller coaster. No one was riding it at the time, the police said.

According to KK Kijima Kogen Operations, which runs the park in Beppu, a city famous for hot spring resorts, it was preparing to put a second roller coaster into service at around 3 p.m. to accommodate a growing crowd. The roller coaster is believed to have been going 40 to 50 kph when it struck the two men, knocking them to the ground some 2 meters below.

The Jupiter is Japan’s first wooden roller coaster, according to the park’s website. It was built from 60,000 Douglas fir trees.

Kijima Kogen President Toshiaki Shiga apologized at a news conference the same day, admitting there was “a lack of information sharing” among the staff because track inspections aren’t supposed to be conducted when a roller coaster is being tested.

The company said on its website that the Jupiter has been suspended so a thorough investigation of the accident can be conducted.