A seismic fault running underneath a nuclear plant in western Japan is likely to be active, which could force the scrapping of one of its two reactors, according to a team of geologists.

Dozens of police officers on today raided the offices of Kansai Electric at the site of Japan’s worst nuclear plant accident as part of a criminal investigation into the tragedy that killed five people last month, an official said.

Smoke billowed from an experimental nuclear power plant in central Japan today, but there were no initial reports of radiation leaks or injuries.