OSAKA -- A "sokaiya" corporate racketeer arrested on suspicion of receiving illegal payoffs from Kobe Steel Ltd. was found to be holding stocks of about 500 companies worth about 400 million yen in market value, sources said Friday.

The massive portfolio of Kazuo Okuda, 57, came to light after investigators studied the statements he gave the investigators as well as confiscated documents, the sources said.

Authorities were probing the sources of funds he used to purchase the stocks and Okuda's relationship with those companies, they added.

The documents confiscated from Okuda's office in downtown Osaka, which included invitations to shareholder meetings, filled four cardboard boxes and four paper bags.

According to the investigators, the list of Okuda's stockholdings covered various industries, including those of banking, construction, pharmaceuticals, distribution, and hotels, in addition to about 14,400 stocks in Kobe Steel.

His portfolio was mostly made of up of units of 1,000 stocks, the minimum necessary to be eligible to attend shareholder meetings, according to the sources.

Prior to Friday's findings, investigators had found stocks of about 250 firms, mainly located in Osaka Prefecture, in Okuda's possession.