Soviet-era incendiary bomb found in Riihimäki could have caused damage within 10-metre radius

Finnish defence forces are still examining a Soviet ZAB-2.5 incendiary bomb discovered last week in a field in Riihimäki, southern Finland, after preliminary tests confirmed its type and potential hazard range, public broadcaster Yle reports.

The device, unearthed in the Peltosaari district, contains thermite—a flammable compound rather than explosive material—and was capable of igniting a ground fire or causing severe burns to anyone within a 10-metre blast radius, according to Häme Police Sergeant Teemu Lehmusvaara. While the bomb’s fuse had functioned, it failed to detonate when originally dropped during wartime.

Lehmusvaara stressed that the bomb, exposed to soil conditions for decades, had not become more volatile over time. Its corroded casing, however, made it impossible to assess stability without expert handling. Authorities warned that even minor disturbances could have triggered the device, though Lehmusvaara declined to speculate on specific risks like movement or shaking.

The bomb went unguarded for nearly 24 hours after its discovery, during which a man—now under investigation for explosives offences—allegedly moved it. Police also face scrutiny for failing to secure the site immediately; a separate complaint has been filed with the national prosecutor’s office over their delayed response to an initial report in April.

Defence forces will destroy the bomb once investigations conclude. Authorities reiterate that unexploded ordnance must never be touched, as surface-level assessments cannot determine safety. The original finder is not suspected of wrongdoing.