A man and woman have died in a decompression chamber at a Japanese hot spring spa in the Saitama prefecture, north of Tokyo.

A 65 year-old man and 58 year-old woman were found collapsed on Sunday in the dome-shaped chamber named “Pascal Health Cell” at the facility called Manainoyu in the city of Fujimino.

The chamber reduces air pressure to levels equivalent to those found at a height of 3,500m (11,550ft) above sea level – helping to increase energy consumption.

The door to the chamber was timed to open automatically after 45 minutes, but the two victims were discovered 50 minutes after the programme began with the door still shut, according to local media.

Police are investigating the cause of death.