Steelmaker NKK Corp., now known as JFE Engineering Corp., is suspected of using some 500 million yen in undeclared income to quell opposition to its construction of two waste incinerators.

Sources said Friday that NKK resorted to such tactics as paying off gangsters.

NKK allegedly falsely declared the money as deductible expenses in the three years to the end of March 2003. The sources said some of the cash went to underworld groups involved in protests targeting incinerator projects.