A federal probe has been launched regarding the ties between Sen. Robert Menendez (D-N.J.) and two internationally wanted Ecuadorian bankers, NBC 4 New York reports. The investigation involves a possible exchange of favors for campaign contributions. Senator Menendez’s office has denied knowledge of any investigation into the matter.

Menendez, the chair of the Foreign Relations Committee, reportedly made phone calls to federal officials in support of the fugitive brothers’ permanent U.S. residency. The feds are investigating whether or not those calls were made in exchange for campaign donations.

The bankers, William and Roberto Isaias, are wanted in Ecuador for embezzlement after they allegedly fled the country with up to “100 million dollars” following the collapse of their bank. In 2005, the U.S. ambassador to Ecuador recommended they be deported to Ecuador, but the Department of Justice says the Ecuadorian government has not provided enough evidence to warrant an extradition. Interpol issued international arrest warrants for the brothers in 2010.

As non-residents, the Isaias brothers cannot donate to a U.S. political campaign, but relatives of the brothers did donate more than $10,000 to Menendez himself and $100,000 to the Democratic Party in 2012.

Menendez’s office told The Hill the allegations were false and that the office was unaware of any such investigation. Menendez’s communications director, Tricia Enright, said, “A year after a false smear campaign was launched against Senator Menendez, once again we see anonymous sources making outlandish allegations.”

Enright was referring to a separate investigation into Menendez’s relationship with Dr. Salomon Melgen, with whom he allegedly traded his political weight for campaign donations.

Enright maintains that Menendez did offer his support to the brothers, but because he believed the Isaias family was politically persecuted in Ecuador for views critical of the government. The brothers’ attorney, Xavier Castro Munoz, also says they are innocent of any wrongdoing, explaining “that is the problem of the Isaiases, that they have committed the crime of being rich in a poor country.”

Scott Fredericksen, an attorney who prosecuted corruption cases for the Justice Department, told NBC 4 New York, “If the government when they look at this, can establish that in exchange for donations from citizens not form this country, of gifts, that the senator took official action that benefited them, now, now we’re talking about something illegal.”

Senator Menendez served in the House of Representatives from 1993-2006 and has been a New Jersey senator since 2006. He was recently re-elected in 2012.