Following the explosion on 19 June at a spa in central Tokyo, Japan, there have been calls for better government regulations to ensure the safety of all spas against accidental explosions.

The blast, at an annex to the women-only spa located near Tokyo’s Shibuya Station, killed three women and injured eight people.

According to The Japan Times, it is suspected that the explosion was caused by methane gas trapped inside the annex building exploding, although a gas separator had been fitted to the annex. The water at the spa was also piped from depths underground of 4,921ft (1,500m).

There is also a strong possibility that executives of the spa operator were unaware of the danger of methane gas at the facility.

There are 148 spa facilities in Tokyo, all located on top of the Southern Kanto Gas field.