Melgen is involved in numerous businesses, all sharing the same address in West Palm Beach, according to records filed with the Department of State in Florida.
Late Tuesday and early Wednesday, FBI agents were seen inside the West Palm Beach building, walking its halls and standing beside shelves full of files.
The Daily Caller began publishing stories on its website about Menendez and Melgen on Nov. 1, when it reported that two women from the Dominican Republic said Menendez paid them for sex earlier in 2012. Prostitution is legal in the Caribbean nation.
Melgen is listed as having an ownership interest in DRM Med Assist, which Federal Aviation Administration records show is the owner of a CL-600 Challenger plane. Flight records for the aircraft were not immediately available.
Melgen, a registered Democrat, has made $193,350 in political contributions since 1998, including $14,200 to Menendez, according to Federal Election Commission records. Menendez was chairman of the Senate Democratic Campaign Committee, which raises money for Democratic Senate candidates, from 2009-2011.
Menendez, a lawyer, is a former mayor of Union City, N.J., and also served in the New Jersey state General Assembly and the New Jersey state Senate. He is divorced and has two children.
Melgen, 58, is a native of the Dominican Republic, where he earned his medical degree from the Universidad Nacional Pedro Henrquez Urea in 1978. He has lived in the U.S. since at least 1980, holding an internship, residency and fellowship at hospitals in Connecticut, Missouri and Massachusetts, according to records filed with the Florida Department of Health.
Melgen has been licensed to practice in Florida since 1986 and purchased the West Palm Beach plot of land where he built his main office in 1991. Over the years, Melgen has become regarded as a top ophthalmologist, speaking at conferences and even operating on then-Gov. Lawton Chiles in 1997. The governor later appointed Melgen to a state panel on HMOs.
Calls to Melgen's offices Wednesday were forwarded to an answering service where receptionists told callers to try back Thursday. Calls to Melgen's home in North Palm Beach, which is appraised at $2.1 million, went unanswered.
On the website for his medical practice, Melgen writes: "I am always asked what sets me apart from most other doctors, and I would have to say that I do not consider myself to be a `cookbook' physician. My patients are my number one priority, and when I am looking to treat a diagnosis I try to look at all the data at hand and extrapolate the best treatment instead of solely adhering to what the current `standard' of treatment may be."