Buried amid the records compiled in the recently concluded criminal probe of Republican Congressman David Rivera is a $50,000 mystery.

Why did an obscure Republican organization pay $25,000 in 2006 to a defunct company founded by Rivera’s mother? Why did a political consultant with close ties to Rivera receive another $25,000 on the very same day? And where did the money come from in the first place?

Further adding to the mystery: The Republican Party of Florida reportedly made a $50,000 payment to a Central Florida nonprofit group — money the group never received — on the same day the payments went to Rivera’s mother and consultant. Are the payments connected?

These questions are among many left unanswered after an 18-month investigation of Rivera’s finances by the Florida Department of Law Enforcement and the Miami-Dade State Attorney’s Office, a probe prosecutors concluded last month without filing charges against the Miami lawmaker.

Investigators suspected Rivera of misusing campaign funds and concealing money he received while working as a consultant for a dog track seeking voter approval for slot machines in Miami-Dade County. Rivera, who was elected to Congress in 2010 after eight years in the Florida House of Representatives, has denied any wrongdoing, and lambasted the investigation as flawed. He remains under investigation by the FBI and the Internal Revenue Service.

In a statement issued through his campaign, Rivera said the $50,000 was spent on a “voter outreach program” coordinated by the Miami chapter of the Republican National Hispanic Assembly, a little-known Hispanic group. Rivera also provided records of absentee-ballot materials mailed to voters under the Hispanic Assembly’s name.

However, neither GOP officials nor Hispanic Assembly members recall such a campaign. And Rivera’s mother told prosecutors in a sworn statement that her company — described by prosecutors as “non-existent” — never did any work that she could remember.

Loans and financing

As part of the state probe, FDLE agents gathered bank records of Rivera and of those close to him — including his mother, 71-year-old Daisy Magarino, and Esther Nuhfer, a political consultant and fundraiser whose firm received more than $800,000 from campaigns and committees tied to Rivera, records show.

FDLE investigators found that Rivera’s finances were often entangled with those of Magarino, her business partner — who is Rivera’s godmother — and their companies. For example, Rivera arranged for one of his mother’s companies to receive more than $500,000 from the former Flagler Dog Track, now called the Magic City Casino. Rivera later received $132,000 in loans from his mother’s company — loans Rivera never listed in state financial disclosure forms.

Among the bank accounts scrutinized by the FDLE was one for Millennium Marketing Strategies, a company founded by Magarino in 2000.

On Aug. 31, 2006, the company received a $25,000 check from the Miami chapter of the Republican National Hispanic Assembly of Florida. A note on the check said it was for “grassroots organization.”

Millennium was a would-be marketing company dormant since 2001, state records show. When questioned by prosecutors last August, Magarino conceded that Millennium Marketing Strategies was “almost a non-existent company,” and she said she could not remember any work the company did.