Two former investment executives from Japan pleaded not guilty in Las Vegas on Thursday to criminal fraud charges in what prosecutors have called a $1.5 billion international Ponzi scheme.

Junzo Suzuki, 70, and his son, Paul Suzuki, 40, arrived in custody in the U.S. on Wednesday, and appeared before a federal magistrate who set a hearing next Wednesday to decide if they will be freed from jail pending trial.

Their attorneys, Richard Wright and Junji Suzuki, declined to comment outside court. Junji Suzuki said he is not related to the defendants.

Junzo and Paul Suzuki were arrested in Japan in January, two months after a federal jury in Las Vegas found their co-defendant, Edwin Fujinaga, 72, guilty of 20 counts of mail fraud, wire fraud and money laundering.

Fujinaga once headed a Las Vegas-based company, MRI International Inc., with thousands Japanese investors-turned-victims.

He is expected to face what would amounting to the rest of his life in federal prison at sentencing, which was postponed last week and reset for May 23. Prosecutors are asking a judge to sentence him to 50 years in prison.

In court documents, U.S. attorneys have compared the case in Las Vegas to the biggest-ever U.S. Ponzi scheme prosecutions: Bernard Madoff's guilty plea in 2009 in New York, Allen Stanford's conviction in Houston in 2012, and Scott Rothstein's guilty plea in 2010 in Miami.

Madoff, now 80, was sentenced to 150 years in prison for bilking thousands of investors out of at least $20 billion. Stanford, 69, is serving 110 years for a scheme involving more than $7 billion. Rothstein, 56, is serving 50 years in a $1.2 billion case.

Court documents say Junzo Suzuki was MRI International's executive vice president and Paul Suzuki managed Tokyo operations.

From about 2009 to early 2013, prosecutors said more than $1 billion in investments from more than 10,000 Japanese investors was wired to bank accounts in Las Vegas under Fujinaga's control. Investors were told they were buying claims from a medical collection business, according to the indictment in the case.

Instead, Fujinaga was found guilty of using new investors' money to pay off previous investors and spending the rest on himself, including a Las Vegas golf course mansion, a private jet, luxury cars and real estate in California wine country, Beverly Hills and Hawaii.

Prosecutors say that when the Japanese government revoked MRI's license to market securities in April 2013, the firm owed investors more than $1.5 billion.