Investigators will go to Seibu Railway group offices this week and press charges against current Seibu executives as well as Tsutsumi, 70, Japan's Kyodo new agency reported on Wednesday. Tsutsumi, who was chairman of Kokudo, the railway company's parent, will be questioned by prosecutors on his role in a statement that allegedly under-reported holdings of major shareholders, said the Nihon Keizai Shimbun.

The executives were also suspected of massively selling Seibu shares before admitting the under-reporting scandal in October - a move that saw Seibu stock nosedive and then led to delisting from the Tokyo Stock Exchange.

Tsutsumi, whose family bought up property as Japan rebuilt after World War II, was named as the world's richest person by Forbes in 1990, with a fortune put then at US$16 billion (HK$124.8 billion). By 2004, he was ranked 159th with US$3 billion.

In October, Tsutsumi quit as chairman of companies including the Tokyo's Prince Hotel, Seibu Construction and Kokudo to take responsibility in the scandal.

Two people have committed suicide over the scandal, including former Seibu Railway president Terumasa Koyanagi, 64. He was found hanged in his Tokyo home last month.

Before killing himself, Koyanagi admitted to prosecutors that a Kokudo executive told him to lie about the financial statement and alleged the order came directly from Tsutsumi, Fuji Television reported.

In June, the Seibu group reported to authorities that Kokudo's shareholding in Seibu Railway was 43.16 percent, although Kokudo actually held a 64.83 percent stake, previous reports had said. As a result, the group was able to hide the fact that the top 10 major shareholders held more than 80 percent of the group - a criteria for delisting from the Tokyo market.

From August to October, Seibu executives and Tsutsumi reportedly sold some 65 billion yen (HK$4.87 billion) worth of Seibu Railway shares held by Kokudo to 72 companies and individuals in off-market transactions.