Methane gas at potentially explosive concentrations was detected at the EXPO 2025 Osaka-Kansai site, where a test run was being conducted on April 6.

According to event officials, the fire service was informed on April 6 at around 4:00PM that methane gas was detected on the west side of the Expo site.

When firefighters and officials checked the underground electrical equipment space, they found methane gas in concentrations that could be explosive if mixed with air and ignited.

The area was ventilated for 30 minutes and found to be safe, but this location had previously been observed to have exceeded acceptable values.

Event officials have said they would like to learn from this and take firm action in the run-up to the event, and that a fence will be put up around the area to prevent access.

Measures had been taken at the venue following a methane gas explosion at a toilet construction site in March 2024.