A former aide of U.S. Rep. David Rivera and a printing company have both become witnesses in the federal investigation of the Republican politician’s ties to an illegally funded congressional campaign, The Miami Herald and El Nuevo Herald have learned.

The cooperation of former Rivera aide Ivette Pinto and Expert Printing & Graphics in Doral mark another major milestone in a criminal case that has already resulted in the guilty plea of Democratic congressional candidate Justin Lamar Sternad.

Fueled with at least $81,486 in secret money, Sternad’s campaign was used as a proxy to undermine a political rival of Rivera, who denies wrongdoing.

Sternad was cooperating with prosecutors even before he formally admitted Friday that he illegally accepted secret money, lied about it and schemed with as-yet unnamed coconspirators. In a written statement, he said he was “used by others.”

Now Expert Printing, which produced Sternad’s mailers, said they worked directly with Ana Alliegro. She was Sternad’s campaign manager and is a close friend of Rivera.

“We were hired by Ana Alliegro to Design & Print Campaigns Flyers for Justin Lamar Sternad and received full payment for services rendered,” according to a statement from the company emailed to the newspapers.

Alliegro’s public whereabouts have been unclear since she skipped out on a meeting with FBI agents in October.

Key player

“Expert Printing has been fully transparent and [is] cooperating with authorities since the initial stages of this case,” the statement also said. “Expert Printing has been and will continue to fully cooperate and or assist the FBI or any other Legal entity or authority investigating this case now and in the future.”

Expert Printing is a key player in the Sternad case and his candidacy. It likely knows who delivered $15,000 in unreported cash and when.

The company is a longtime vendor of Rivera’s and other Republican candidates, and may have produced about a dozen different types of mailers for Sternad, a Cutler Bay political newcomer and unknown who had no money to pay for it all.

One Expert Printing-produced mailer for Sternad echoed a line of attack, originating with Rivera, that savaged rival Joe Garcia over his divorce. Garcia, a Democrat, beat Sternad in the Aug. 14 primary and then defeated Rivera, a Republican, in November to capture the new Kendall-to-Key West congressional seat.

About the same time that Expert Printing was working for Sternad, it was approached to do a small print job by a little-known nonprofit Hispanic advocacy group called Florida Action Network, for which Pinto helped keep the books.

The FBI is examining whether the money for Florida Action Network was diverted to help underwrite some of Sternad’s campaign. Two network founders told the newspapers they never saw the mailers.

Neither Pinto nor Expert Printing would say if Florida Action Network’s mailer was ever produced or if its money was illegally spent to help Sternad.

“To be clear, Ms. Pinto has done nothing illegal and has cooperated fully with federal law enforcement in its investigation as a witness,” her lawyer, Robert H. Fernandez, said in an email.

Fernandez helped incorporate Florida Action Network in April 2012. The nonprofit had relatively little money last year when it decided to spend less than $14,000 with Expert Printing to make a mailer to get out the Hispanic Republican vote in Miami-Dade County.