According to Tokyo police, a female employee was killed after the seat section of the "Flying Balloon" amusement ride at Tokyo Dome City Attractions fell onto her during maintenance work on April 21.

The attraction was manufactured in Italy and uses hydraulic pressure to control the vertical movement of the seats.

Investigative sources said security camera footage shows that no one was in the ride's control room at the time of the accident, and there were no signs that the control panel had been touched.

The sources said on-site inspections indicate that oil was leaking from a valve that regulates hydraulic pressure.

The oil leak is believed to have weakened the force supporting the seat section, causing it to fall.

Police are investigating what caused the oil leak.