The sum is six times the amount initially confirmed by Reuters and could, if found to be bribery, result in Okada being stripped of his firm's casino license in the Philippines and also jeopardize his gaming license in Las Vegas.

A Hong Kong firm established by Okada's Universal sent the money to Manila-based consultant Rodolfo Soriano in a series of payments in the first half of 2010, according to a review of company records and interviews with more than a dozen current and former employees and people familiar with the investigation.

Soriano, who has close ties to key members of the administration of former Philippine President Gloria Macapagal-Arroyo, received the payments as Universal was lobbying for tax and other government concessions to boost the profitability of a $2 billion casino it was developing on Manila Bay.

Soriano is now under investigation by the Philippine Department of Justice which has created an inquiry panel on the payments with a target to submit findings within the next month.

Universal, a Tokyo-based maker of gaming machines majority owned by an Okada family trust, had no comment through its lawyer, Yuki Arai. Soriano could not be reached for comment.

In addition to the investigation in the Philippines, the Universal payments are being probed by U.S. gaming regulators, with the Nevada Gaming Control Board likely to call the 70-year-old billionaire to give evidence at a closed-door investigative hearing, people familiar with the matter said.

Soriano's powerful connections included Arroyo's husband, Jose Miguel, with whom he had travelled to Las Vegas in 2009.

Soriano was an early partner in Okada's Philippine project, and Universal documents describe him as the "personal secretary" to Efraim Genuino, former head of gambling regulator the Philippine Amusement and Gaming Corporation (PAGCOR).

Jose Miguel Arroyo, a lawyer by training, could not be reached for comment. His spokesman, lawyer Ferdinand Topacio, said he was unaware of any business dealings between Jose Miguel Arroyo and Soriano. "We are denying reports linking Attorney Arroyo to that bribery case," Topacio said.

Genuino's lawyers did not respond to calls seeking comment. PAGCOR has said it has no knowledge of the Soriano payments but is cooperating with the Philippine bribery investigation.

The Universal payments to Soriano in 2010 were described at a company meeting as a "completion bonus" for his help in clearing remaining hurdles for the casino, including an exemption from corporate tax and foreign ownership restrictions, people involved in the project said.

Philippine authorities have already threatened to strip Okada's operating company of its casino license if investigators find evidence of bribery. Nevada regulators could also impose sanctions, including a suspension of Okada's Las Vegas license.

Either outcome would represent a major setback for Okada, who has vowed to bounce back from a costly legal fight with American casino magnate Steve Wynn to turn Universal into Asia's leading operator of high-end casino resorts.

In the United States, the FBI has also taken statements from those involved in the Soriano payments, according to people familiar with that inquiry. The bureau declined to comment on the state of its inquiry.

LUCRATIVE CONCESSIONS

The Nevada Gaming Control Board's investigation has been underway since at least August and is gathering momentum.

"We are continuing our work," board chairman A.G. Burnett said, declining to comment on the agency's next moves or the likely conclusion of its investigation. "We're about in the middle stage of our investigation."

Hearings could help the board's three-member investigative panel decide whether to bring a formal complaint against Okada or his company, the people familiar with the investigation said.

Investigators were particularly concerned about fund transfers to Soriano-controlled Subic Leisure and Management, registered in the British Virgin Islands, because that jurisdiction allows firms to conceal the identity of directors and investors.

"He's going to have some interesting explaining to do," one of those with knowledge of the investigation said of Okada.

Universal has maintained that at least some of the payments to Soriano were not approved. It has sued three of its own former executives in Tokyo District Court, claiming they made $15 million in payments to entities controlled by Soriano without authorization by Okada or the Universal board.

A review of company records and interviews with sources shows that a total of $40 million was sent by Universal to Soriano-controlled firms. The money was sent to Hong Kong firm Future Fortune, set up as an investment vehicle for the Philippines project. Of the total, $10 million was routed back immediately to Universal for internal accounting reasons, leaving Soriano with a net $30 million.

It is not clear how that money was invested or disbursed.

Gloria Macapagal-Arroyo's government gave Universal a corporate tax exemption in March 2010, leaving the casino liable only for a 23.5 percent gaming tax. That exemption was key to the projected profitability of the casino, which had been given a provisional license in 2008.

As a result of the tax concessions and low labor costs in the Philippines, Okada told investors and analysts last year that the Manila casino would be more profitable than gaming in Macau or Las Vegas, markets where Wynn has built his resorts.

The investigation of the payments to Soriano threatens to complicate Okada's efforts to recover from a costly falling-out with U.S. casino tycoon Wynn.

Okada was Wynn's largest investor until the American accused him this year of improperly paying $110,000 in entertainment and other expenses for gaming regulators from the Philippines and Korea, where Okada is also looking to build a casino.

As a result of the disclosures, Wynn forced Okada to redeem his 20 percent stake in Wynn Resorts for $1.9 billion, a 30 percent discount to the market value.

Okada has sued to reverse the redemption, saying Wynn forced him out for questioning Wynn Resorts' dealings in Macau.

The Nevada Gaming Control Board has been separately investigating Wynn Resorts on allegations made by Okada that Wynn's company sought to influence Macau officials through a donation to the University of Macau, the people close to the matter said.

However, this probe was likely to be resolved without an investigative hearing, they said, signaling that Wynn Resorts was less likely to be subject to a major disciplinary action.

(Additional reporting by Taro Fuse, Kevin Krolicki and Takeaki Ueno in Tokyo, Manuel Mogato in Manila, Sue Zeidler in Los Angeles and Farah Master in Hong Kong; Editing by Mark Bendeich)

• A Permanent Economic Emergency