An inquiry into corner-cutting at a polluted site selected to become Tokyo's main wholesale foods market has failed to identify who changed construction plans and why.

The findings, announced Friday, led to an infuriated Tokyo Gov. Yuriko Koike proposing protections for whistleblowers to prevent such cover-ups.

She said the probe failed in its principal aim: to determine why a thick layer of clean soil was never laid at the site. Instead, empty basements are now subject to water welling up and bringing with it toxins such as arsenic, cyanide and benzene.