Tokyo police launched a criminal investigation Monday into Mitsui & Co. and one of its subsidiaries, suspecting that the giant trading house fabricated test data to obtain official approval for a diesel particulate filter.
Investigators searched Mitsui's headquarters and its DPF-manufacturing subsidiary, PUREarth Inc., both located in Tokyo. They also searched some other 20 sites in connection with the probe.
Mitsui announced Nov. 22 that it had submitted the fabricated data in 2002 to obtain approval for the device, which removes particulate matter from diesel engine exhaust, and to meet clear-air standards set by Tokyo and three neighboring prefectures.