A grand jury is investigating New Jersey Democratic Sen. Bob Menendez’s ties to Democratic Party mega-donor Dr. Salomon Melgen, the Washington Post reports.

The Post’s Carol Leonnig and Peter Wallsten cite “three people aware of the probe” as saying a Miami federal grand jury has launched an investigation into Menendez’s activity in government advocating in favor of business interests of Melgen, including the now infamous port security contract that would make Melgen $250 million over a decade if approved.

“As part of the grand jury investigation, the three people said, federal agents have questioned witnesses about the interactions between Menendez and Melgen, who contributed $700,000 last year to Menendez and other Senate Democrats,” Leonnig and Wallsten wrote. “The grand jury has also issued subpoenas for Melgen’s business and financial records, according to two people briefed on the probe who, like the others, spoke on the condition of anonymity to describe an on-going investigation. Federal agents have not contacted Menendez, according to a person familiar with the case.”

The Daily Caller confirmed the Washington Post’s report, citing an “FBI agent in a supervisory position on the East Coast of the U.S.”

That agent said, according to the Caller, “he is aware of investigative reports sent from the bureau to the U.S. Attorney’s office in Miami, Florida, in connection with a grand jury investigation into New Jersey Sen. Bob Menendez.”

The Caller cites a second FBI source, a recently retired agent, as someone who “also confirmed the investigation and the grand jury.”

Leonnig and Wallsten at the Post cast doubt on the investigation, and whether it would lead anywhere. “Cases of political bribery are extremely hard to build and prove, according to ethics experts and public-corruption defense lawyers, and many such investigations fizzle with prosecutors never bringing charges,” they wrote.

They also heavily quoted “veteran defense lawyer” Stan Brand as throwing water on the potential outcome of the investigation.

Both Leonnig and Wallsten have been personally involved in Washington Post misconduct on the Menendez scandal. Leonnig deceptively edited a story last week at least two times without telling readers she did so and Wallsten reported a month-old story as news in what appears to have been an effort at narrative reconstruction by Menendez’s office.