Three people knowledgeable about the grand jury investigation said federal agents have questioned witnesses about interactions between Menendez and Florida ophthalmologist Salomon Melgen, who contributed $700,000 last year to Menendez and other Senate Democrats, the Post reported Thursday.
The grand jury has issued subpoenas for Melgen's business and financial records, two other people briefed on the probe said.
Menendez, who heads the Senate Foreign Relations Committee, acknowledged in January he failed to disclose two free trips he took on Melgen's private plane to vacation with him in the Dominican Republic in 2010. Menendez said he later wrote Melgen a personal check for $58,500 to reimburse him for the rides.
The Senate Ethics Committee is investigating why Menendez did not disclose the trips sooner.
Documents and interviews indicate Menendez has intervened on issues that could affect Melgen's financial interests, such as seeking to apply pressure on the Dominican Republic government to honor a contract with Melgen's port security company. Menendez's office has acknowledged he interceded with federal healthcare officials after they said Melgen overbilled the U.S. government for care at his clinic.
Menendez declined to tell the Post whether he knew anything about the investigation, but said he welcomed the review.
"I welcome any review, because I believe, at the end of the day, that my actions have been appropriate," he said. "And just as everything that gave rise to this was a smear campaign based on slanders that drove the original story, I believe that when any review reviews the facts, they will determine that I have acted appropriately at all times."