The civil case in which Fujihara submitted his statement, at the request of Okada's lawyers, stems from a prior business relationship between the two casino titans that soured when Wynn dismissed Okada from the board of Wynn Resorts in 2012. At the time, Wynn claimed that Okada had spent over $100,000 to wine and dine and provide gifts to Philippine gaming officials, and filed suit claiming the Japanese billionaire had breached his duties as a director. Okada said the payments were not illegal and that his ouster was unjustified.

The criminal bribery investigation into Okada was initiated after Wynn filed its civil suit, according to people familiar with the probe. In a statement responding to Fujihara's assertions, the Wynn Resorts head of security, James Stern, said that he reported to FBI agents in Las Vegas around March 2012 that former Okada employees had contacted him with allegations of wrongdoing more serious than those in the civil suit.

Stern, a former FBI agent himself who had postings in Tokyo and speaks Japanese, said in his statement that he was later contacted about a current Okada employee willing to talk. Stern said his first encounter with Fujihara was in late November 2012 in a hotel room at the ANA Intercontinental Hotel in Tokyo.

Stern said he "explained that Wynn Resorts and I were cooperating with the government's criminal investigation, and inquired whether Mr. Fujihara was willing to speak to and meet with investigators from the FBI."

He said Fujihara agreed to his request. Stern said he then "coordinated arrangements" for Fujihara and another former Okada associate, Toshihiko Kosaka, to travel to San Francisco to meet with the FBI. Kosaka did not respond to a request for comment.

It was a role well suited to Stern, an expert interrogator who had contacts within the Japanese police and was head of Asia organized crime at the FBI before joining Wynn in 2007. All told, he connected 11 current and former Okada employees with the FBI by making introductions, organizing flights, scheduling meetings, and covering expenses for these potential witnesses on trips from Japan to locations such as Los Angeles, Hawaii and Guam, according to people familiar with the situation.

Wynn Resorts spent more than $100,000 on travel, meals and accommodations for the potential witnesses, according to an Okada court filing that cited Wynn Resorts expense reports.

The total number of witnesses Stern brought to the FBI has not been disclosed in the ongoing civil case. Fujihara is the only former Okada associate to submit a statement to the court.

Paying for travel

Overseas corruption probes are difficult for the United States to conduct because of language differences, the challenges and costs related to locating and interviewing witnesses, and other issues, legal experts said. As a result, the government leans on companies that are subject to the FCPA to uncover and report foreign bribes on their own, and corporations often assist investigations into wrongdoing by their own employees or when they believe they are a victim of a crime, the experts said.