A potentially explosive concentration of methane gas has been detected at the site of the 2025 World Expo in Osaka Prefecture, prompting safety measures and raising fresh concerns about the artificial island where the event will be held.
The Japan Association for the 2025 World Exposition said Monday that methane levels exceeding safety standards were found in an underground utility pit on the western side of the Yumeshima venue, where electrical equipment is installed.
The Osaka Municipal Fire Department received a report around 4 p.m. Sunday and temporarily restricted access to the area while ventilating it by opening nearby manholes.
A three-day test run involving visitors had been held at the venue from Friday to Sunday ahead of its grand opening next Sunday.
Methane is highly flammable, and if ignited, can cause explosions.
The association said it would increase the frequency of gas monitoring in response to the incident.
Yumeshima, the manmade island in the city of Osaka hosting the event, was partially built on landfill containing industrial waste, a condition known to promote methane formation.
In March 2024, a spark from welding work in a restroom triggered an explosion after igniting gas that had accumulated beneath the floor, damaging concrete and other infrastructure. Following that accident, the expo organizers introduced regular gas monitoring and ventilation protocols.
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