A former Mitsui & Co. employee and the former vice president of an affiliate pleaded guilty Wednesday to falsifying test results for diesel exhaust filters it sold to the Tokyo Metropolitan Government for some 57 million yen.

Yuji Shiro, 47, former head of Mitsui’s high-technology business section, and Tetsuro Toyoda, 48, former vice president of PUREarth, entered their pleas at their first trial session before the Tokyo District Court. Shiro was sacked by the major trading house after the scandal broke, while Toyoda resigned.

The trial concluded with prosecutors demanding two years in prison for both defendants.