FBI investigating prostitution claims against Sen. Menendez

(CBS News) New Jersey Senator Robert Menendez, chairman of the Foreign Relations Committee, is currently overseas leading a congressional delegation. Back at home he has been fighting off various allegations of wrongdoing, all related to his ties to a Florida doctor who is a major campaign contributor.

CBS News can confirm that the FBI is looking in to the claims, including one that the Senator solicited prostitutes while on a trip to the Dominican Republic - a country where prostitution is legal. So far the investigations have not been able to prove that Menendez did anything wrong, but with every charge, the pressure is growing on Menendez.

Senate Ethics Committee investigating Menendez

The Miami herald dispatched a team of reporters to the country to investigate. "Trying to find someone this many months after the fact based on all the sketchy allegations and the unclear claims, its really difficult. It's a cold trail," said Marc Caputo, a political writer for the paper. "But that's only part of what's become a steady drip of allegations against Menendez."

The FBI and the Senate Ethics Committee also are investigating Menendez's relationship with Florida doctor Salomon Melgen, a close friend and campaign contributor. Last month, the FBI raided Melgen's West Palm Beach office after the doctor was accused of improperly billing Medicare nearly $9 million. He is fighting those charges.

Menendez's office confirmed it contacted U.S. health agencies to see if the charges against Melgen could be disputed and he's repeatedly denied interfering with any investigations.

"I welcome any review. But I have no intention of having the smears try to deviate me from the work that I have been doing and will continue to do," said Menendez.

Senator Menendez intern arrested, was illegal immigrant and registered sex offender, report says

Menendez also is accused of trying to help Melgen by discouraging the State Department from donating port security equipment to the Dominican Republic.

Melgen held a lucrative private contract to provide the equipment and would have an obvious interest in not seeing the government provide it for free.

"If the FBI believes it can show that Sen. Menendez actually traded favors in return say for campaign contributions or that he intentionally falsified documents like his financial disclosure forms, then they could charge him with a crime. But those are really high bars to meet," said Caputo.