Updated

A senior U.S. Navy criminal investigator tipped off an Asian defense contractor at the center of a multimillion-dollar fraud investigation and downloaded more than 100 confidential files in exchange for luxury trips and prostitution services, prosecutors said.

John Beliveau II will plead guilty to bribery charges Tuesday in federal court in San Diego, his attorney Jan Ronis said. Beliveau could face a maximum sentence of 20 years.

The conviction would be a first for federal prosecutors in the massive scandal that has ensnared six Navy officials so far and could lead to an expansion of the probe if Beliveau cooperates with authorities as part of his plea agreement.

Prosecutors say Leonard Francis, 49, the CEO of Singapore-based Glenn Defense Marine Asia Ltd., or GDMA, overbilled the Navy by at least $20 million. They said the scheme included giving bribes to Navy officers who would provide Leonard with confidential ship route information or direct the movement of Navy vessels to Asian ports with lax oversight so the company could inflate costs and invent tariffs by using phony port authorities.

"This isn't only bad news for Leonard Glenn Francis, but I suspect there are a number of yet unnamed Navy people who are (and should be) worried," Michael T. Corgan, a Vietnam veteran who teaches international relations at Boston University, said in an email.

"Something of the scope that this scandal embraces didn't happen without a reasonably widespread acceptance of bad practice," he wrote.

In exchange for the assistance from the Navy officials, Francis, known in military circles as "Fat Leonard," lined up prostitutes, hotel stays and tickets to shows, including a Lady Gaga concert in Thailand, according to a criminal complaint.

Francis, who was arrested in September, and his cousin, Alex Wisidagama, a company manager who was also arrested, have pleaded not guilty to charges in the case. Navy Cmdr. Jose Luis Sanchez and Cmdr. Michael Vannak Khem Misiewicz also have pleaded not guilty.

GDMA has provided fuel, food and supplies for Navy ships for 25 years. The investigation started in 2009.

According to the complaint, Beliveau, 44, kept Francis abreast of the Navy's probe and advised him on how to respond. He downloaded at least 125 sensitive records from the case files of his fellow Naval Criminal Investigative Service agents, according to charging documents.

The two exchanged thousands of text messages, and at one point, Francis bragged to an associate in an email: "'I have inside Intel from NCIS and read all the reports,"' according to court documents.