A U.S. asset management firm is suspected of mishandling the funds of thousands of Japanese clients in a debacle that could add up to losses of more than ¥130 billion, sources familiar with the matter said Friday.

The Securities and Exchange Surveillance Commission raided the Tokyo office of Nevada-based MRI International Inc. and other related locations in the afternoon for evidence for prosecutors.

Investigations by the commission so far show that most of the funds are missing and MRI International may have lost them, the sources said.