In letters sent to lawmakers and Obama administration officials, the head of Reflex Responses, a company based in Abu Dhabi, said that Mr. Prince “has no ownership stake whatsoever” in the business.
“He is not an officer, director, shareholder, or even an employee of R2,” wrote the company’s president, Michael Roumi, referring to the company by its common name.

Mr. Roumi’s letters, dated May 18, were sent in response to inquiries by members of the House of Representatives after The New York Times reported last month that the United Arab Emirates had signed a $529 million contract with R2 to build the foreign battalion. According to American officials and former company employees, the crown prince of Abu Dhabi hopes to use the foreign troops to put down labor unrest in the country and defend the U.A.E. from terrorist attacks. One of Mr. Roumi’s letters was passed to a group of congressmen by Victoria Toensing, Mr. Prince’s lawyer.

The Justice Department has opened an inquiry into whether the company may have violated United States laws prohibiting Americans from transferring military technology or expertise overseas. Investigators have interviewed at least one former R2 employee, according to two people familiar with the inquiry.

American officials and several former company employees said Mr. Prince was deeply involved last year with R2 and in recruiting contractors to train the foreign troops, The Times reported. Mr. Prince’s current relationship with the company remains unclear.

Five former employees, speaking on condition of anonymity because they had signed confidentiality agreements, said Mr. Prince had overseen the hiring of American military and law enforcement veterans for the project, as well as European and South African contractors. They said he made occasional trips to the desert camp where the foreign troops, many of them Colombians, were being trained. And some of R2’s top managers had worked with Mr. Prince at Blackwater.

The former employees said that Mr. Prince took pains to mask his role in the operation, and that his name did not appear on contract documents between R2 and the U.A.E. that were provided to The Times. R2’s origins and affiliations are unclear; most corporate records are not public in Abu Dhabi. R2’s commercial license lists two other companies as partners, and the name of a third business was posted outside the office suite R2 had been using in the last year.

American laws governing the export of defense technology are murky, but American citizens involved in training foreign troops run legal risks if the State Department does not grant permits for the training. A State Department spokesman said the Obama administration was aware of R2’s operations, but would not say whether the company was operating with licenses from the department.