By Sarah N. Lynch

WASHINGTON (Reuters) -- The top Democrat on a U.S. House of Representatives investigative panel is requesting interviews with a handful of executives at Valeant Pharmaceuticals International who were directly involved in the operations of specialty pharmacy Philidor, according to a letter seen by Reuters.

In the Nov. 16 letter, House Oversight Ranking Democrat Elijah Cummings asks Valeant CEO J. Michael Pearson to make employees Gary Tanner, Bijal Patel, and Alison Pritchett available for "transcribed" interviews.

"Troubling new allegations suggest that a group of Valeant employees helped launch Philidor’s business in 2013 and have remained involved in its daily operations," Cummings wrote.

"These allegations suggest that Valeant employees may have been personally involved in questionable billing practices that led Valeant to cut ties with Philidor last month."

Valeant is reviewing the letter and will respond, Valeant spokeswoman Laurie Little said in an e-mailed statement.

"As we have said previously, Valeant’s board of directors has formed an ad hoc committee to review allegations related to the company’s business relationship with Philidor and related matters."

Cummings' letter comes just a few days after Reuters reported about how several top Valeant employees worked closely with the founders of Philidor Rx Services to set up the business and expand its operations.

Two Valeant employees, for instance, were copied on a November 2014 email which contained an attachment explaining how Philidor employees could bill the highest amount an insurance company was willing to pay by resubmitting rejected claims at different price points.

The email, reviewed by Reuters, was sent to Tanner and Patel, who both used pseudonyms for their communications within Philidor. Reuters also reported that Pritchett was involved in building relationships with specialty pharmacies.

Valeant first disclosed its ties to Philidor late last month, amid concerns over the pharmacy's tactics to get insurers to pay for Valeant medications. It has since severed ties with the pharmacy, saying it has "lost confidence" in Philidor after questions about its business practices.

Cummings is one of many Democrats in the U.S. House who have been pushing for hearings to investigate Valeant, among others, over its rising drug prices.

He has been trying to convince the Republican-led committee to issue subpoenas to Valeant, and has previously accused the company of ignoring his requests for information.

A spokeswoman for the oversight committee, MJ Henshaw, said it is still in fact-finding mode and "at this point we don't feel that a subpoena is a necessary step that needs to be taken."

The committee has been actively reviewing drug pricing in general, she said, and has reached out to a number of drug companies to gather information.

"We plan to hold a hearing on this issue early next year," she added.

Earlier this month, meanwhile, the U.S. Senate Special Committee on Aging launched a new bipartisan probe into drug pricing at Valeant and Turing.

Valeant is also facing investigations by prosecutors in New York and Massachusetts over its drug pricing and programs that provide financial assistance to help patients cover out-of-pocket expenses for their medications.

(Reporting by Sarah N. Lynch, additional reporting by Caroline Humer in New York; editing by Nick Zieminski and Alan Crosby)