The stock scandal embroiling the Seibu group was exacerbated Wednesday when its Shizuoka-based railway company said it had been filing false share-ownership reports with authorities for three decades.

Izuhakone Railway Co. said stakes claimed to be owned by some 400 individual investors had actually been held by Seibu group companies, and that the deception was designed to make the number of investors look bigger on paper.

The Tokyo Stock Exchange, on whose second section Izuhakone Railway is listed, has assigned the firm's shares to the monitoring post to warn investors of a possible delisting.