MIAMI -- Sources familiar with MLB's investigation into a Miami-area clinic say MLB investigators have been told that Alex Rodriguez paid a former clinic employee to prevent the release of potentially damaging documents.

Those same sources say that while MLB investigators find the Rodriguez information credible, the investigators have no physical evidence to connect the New York Yankees' star to payments.

The New York Times reported Friday that MLB investigators had evidence that Rodriguez bought documents from a Biogenesis employee, but a source close to MLB's investigation said that was not correct.

If MLB can acquire physical evidence or convince witnesses to give sworn statements, Rodriguez could not only face suspension from Major League Baseball, but possible criminal charges.

As the Miami New Times and "Outside the Lines" reported, Rodriguez is listed in Biogenesis documents as having received thousands of dollars worth of performance-enhancing drugs. "Outside the Lines" also reported in February that Rodriguez was injected with drugs at his home by clinic founder Anthony Bosch.

Sources told "Outside the Lines" that the former Biogenesis of America employee, Michael Porter Fischer, left the company in September after a falling out with Bosch. Fischer, two sources said, had invested $20,000 in the company, but grew disenchanted with Bosch and demanded his money. The sources said Bosch eventually paid Fischer the $20,000, but refused to pay an additional $4,000 that Fischer said he was owed. Sources said Bosch informed Rodriguez that Fischer was threatening to expose the operation, and Rodriguez gave Bosch at least $4,000 "to make it go away."

Sources disagree as to whether Bosch paid Fischer that money, but several sources said a group of men found Fischer, threatened him, took the documents and paid him $4,000. Sources said they believed that those documents were then destroyed, but offered different opinions as to who sent the men.

Fischer could not be reached for comment. MLB officials declined comment, as well.

Terry Fahn, a spokesman for Rodriguez, said Friday night: "Alex flatly denies the allegations.''

Bosch's attorney, Susy Ribero-Ayala, said Friday night her client was not available to comment on the latest allegations, citing "pending civil litigation and a criminal investigation."

When asked for his reaction to the latest Rodriguez story, Yankees manager Joe Girardi said, "It's an MLB issue. I mean, that's my reaction to that."

Sources told "Outside the Lines" that the Florida Department Health has been investigating whether Bosch practiced medicine without a license, though they are not authorized to bring criminal charges and thus would have to partner with a state or local law enforcement agency.

As for allegations that A-Rod paid for medical documents linking him to Bosch's lab, Ribero-Ayala said, "I have absolutely no knowledge of any of that. I really don't have any comment."

Though MLB investigators have been working the South Florida case with vigor since last summer, they have not yet met or scheduled an interview with Rodriguez, who is on the disabled list as he rehabs from hip surgery.

While it is unclear where MLB is headed with its investigation, sources indicated its ability to call witnesses it has paid money to for information could be called into question (or compromised) in any potential court or arbitration proceeding.

Fischer has been one of the most wanted men for some time in the Biogenesis scandal. Numerous former associates of Bosch's say they believe he gave documents to the New Times. After the New Times broke its story in January, a hunt began for Fischer who was described in documents as Biogenesis' marketing director.

Investigators and reporters have showed up at the front door of the Coral Gables home Fischer shared with his mother and older sister. His sister, Suzanne, a former classmate of Bosch's at Epiphany High School, told "Outside the Lines" that Fischer left the house abruptly earlier this fall, saying "Whatever you do, don't answer the door or nothing."

Fischer left behind his two Rottweilers and 300 pounds of dog food, and hasn't returned since. His sister said one afternoon last fall several "goons" with "big muscles" pounded on the door to the house, yelling, "We'll give you money!"

They were not the only callers looking to discuss money with Fischer.

Found at the foot of the door in March, as the dogs could be heard barking aggressively inside, was a business card and handwritten note from an MLB investigator, reading: "Please call -- we know time is $. Call ASAP."

Sources said Fischer has met with MLB investigators, but was described as being "not particularly helpful."

Sources said MLB has documents from Biogenesis, but did not say where MLB investigators got them. While sources said MLB had paid sources to cooperate and provide information, it was not clear whether MLB had paid anyone for documents.