TOKYO (CNN) - An executive of a Japanese securities firm involved in takeover deals by the high-profile Internet startup Livedoor has been found dead, police say.

The executive, Hideaki Noguchi, 38, was found dead on the southern island of Okinawa, according to Kyodo news agency, quoting police in a report Thursday. Authorities said tests would be needed to confirm the cause of death.

Takafumi Horie, the young entrepreneur whose company, Livedoor, is under investigation in Japan.

Kyodo, quoting police in the Okinawa capital Naha, said that Noguchi apparently slit his wrist at a Naha hotel on Wednesday. He was taken to the hospital but died there.

Noguchi worked for H.S. Securities, a company involved in the acquisition of publishing company Money Life by ValueClick Japan, the predecessor of Livedoor subsidiary Livedoor Marketing.

This deal is at the center of the investigation into Livedoor that prompted a massive sell-off on the Tokyo Stock Exchange Tuesday and Wednesday, raising volume levels so much that the TSE suspended trading 20 minutes early because its computer systems were being overloaded.

The Japanese sell-off, aided by weaker than expected earnings for key U.S. tech stocks Intel and Yahoo, was followed by substantial falls Wednesday in other markets, including Europe and Wall Street.

But on Thursday the benchmark Nikkei index rebounded, climbing to close up 2.3 percent.

The Tokyo District Public Prosecutor's office raided Livedoor's Tokyo headquarters and other locations on Monday on suspicion it may have released false information on the Money Life acquisition and earnings.

According to the Nikkei news network, H.S. Securities has not commented on its involvement in the Money Life deal, but said in a statement it believed it had acted within the law on two other deals under scrutiny. H.S. Securities said its offices had also been searched.

Livedoor, headed by the high-profile entrepreneur Takafumi Horie, on Thursday released the results so far of its own internal investigation of the Money Life deal. It defended its decisions and fund-raising steps, including the use of a share swap deal rather than a cash purchase.

Livedoor said it would continue the internal investigation, the Nikkei news network reported.

"We have officially asked Livedoor to submit the findings of its internal investigation by Friday," Tokyo Stock Exchange President Taizo Nishimuro told a news conference on Wednesday.

"We'll have to see that outcome first," Reuters quoted him as saying.

Sources familiar with the situation said the official investigation initially focused on whether Livedoor and Livedoor Marketing had made misleading statements about the Money Life acquisition.

Local media reports, however, said Livedoor was now suspected of acquiring Money Life as well as two other companies expressly so it could beef up its accounts with profits created from the transactions, Reuters reported.

Livedoor and Livedoor Marketing said in a joint statement they believed that they did not have to disclose the acquisition of Money Life when it was bought by an investment fund associated with Livedoor because the fund was not directly controlled by Livedoor's investment unit, Livedoor Finance.

Even if Money Life was treated as a group company, they said, they were unlikely to have been required to disclose the initial acquisition by the fund under Tokyo Stock Exchange rules.

Livedoor later bought Money Life from the fund and disclosed the acquisition then.

Under Horie, a media-savvy 33-year-old, Livedoor has rapidly built up a portfolio of nearly 50 Internet-related businesses.

But Horie has ruffled feathers in conservative Japanese business circles through a failed attempt to take over the Fuji Sankei media group and an unsuccessful run for parliament in the September 2005 general election.

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