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The Yomiuri Shimbun A manhole connected to an underground area, where a high concentration of methane was detected, is seen on Monday in Osaka.
The Yomiuri Shimbun
14:46 JST, April 8, 2025
The organizer for the 2025 Osaka-Kansai Expo said Monday that a high concentration of methane was detected at the site during a rehearsal. The concentration exceeded 5%, a level at which an explosion could have occurred if ignited.
The Japan Association for the 2025 World Exposition, the Expo’s organizer, said it would increase the number of times the concentration of gas is measured.
According to the association, the methane was detected in an underground area where the outdoor electrical equipment is stored in the Green World zone on the west side of the Expo venue in Yumeshima, Osaka City. It is located near the EXPO Arena and is adjacent to restrooms, where an explosion occurred in March last year when the methane was ignited while a worker was welding.
Kenta Teramoto, a member of the Moriguchi City Council in Osaka Prefecture who participated in the test run on the day, reported at about 4 p.m. that methane was detected.
Emergency fire services and other personnel examined the site and detected the concentration of methane exceeding 5%.
People were prevented from getting close to the area from around 4:30 p.m. The manhole connected to the underground area was opened for ventilation, and restriction was lifted about an hour later.
Teramoto brought a detector to the site and measured the concentration of gas inside the manhole.
As the Expo site is a former landfill where incinerated trash and other garbage were thrown away, there is a risk of possible methane emissions.
The organizer has been measuring the concentration of gas once a day at several locations, but it will increase it to three times a day at seven high-risk locations, including the underground area. In addition, barriers will be put in place around the manhole to prevent visitors from approaching.
