WASHINGTON -- Sen. Robert Menendez is being investigated by a Miami federal grand jury for his role in advocating for the business interests of a wealthy donor and friend, The Washington Post reported.

The newspaper reported that as part of the probe, federal agents have questioned witnesses about the interactions between Menendez (D-N.J.) and Florida ophthalmologist Salomon Melgen. The Post said the grand jury also issued subpoenas for Melgen's business and financial records. The newspaper cited unidentified people it said were aware of the probe.

A spokeswoman for Menendez, Tricia Enright, didn't respond to a question about whether the senator is under a grand jury investigation but issued a statement saying, "We welcome any review because Senator Menendez's actions have always been appropriate, and we believe the facts will confirm that." Federal agents have not contacted Menendez, one person told the Post.

The newspaper said Melgen declined to say whether he knew about the investigation, but he said any probe would find no wrongdoing.

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Melgen attorney Kirk Ogrosky said the eye doctor was proud of his relationship with the senator and had no worries about a federal probe.

Menendez and Melgen's overlapping interests have raised questions in recent months. Menendez was compelled to reimburse $58,000 for two flights to the Dominican Republic aboard Melgen's private jet for personal trips in 2010 that he previously had failed to report, prompting scrutiny by the Senate Ethics Committee. -- AP