A top Democrat wants to know what happened to an analysis of the Republican tax reform bill that was repeatedly promised by Treasury Secretary Steven Mnuchin.

Ron Wyden, the ranking Democrat on the Senate Finance Committee, is asking Treasury's internal watchdog agency to find out whether there was any "political interference" with the analysis of the GOP tax overhaul plan according to a letter sent Tuesday. He is also seeking answers about a 2012 economic paper that has disappeared from Treasury's website.

"I am concerned about the possibility that the Treasury Department is burying critical research [in] an effort to mislead the public," Wyden wrote in a letter seen by CNN.

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Wyden said the 2102 economic paper had "contradicted" an assertion made by Mnuchin in September about how corporate tax cuts could ultimately benefit workers.

Earlier this fall, the secretary said "most economists believe that over 70% of corporate taxes are paid for by the workers." However, the paper by the agency's Office of Tax Policy "strongly disputed that conclusion," arguing that workers only end up paying for 18% of corporate taxes. That paper later disappeared from the Treasury Department's website.

Rich Delmar, general counsel for the Treasury inspector general, told CNN the agency is working to incorporate questions posed by the senator into the agency's ongoing review.

Delmar didn't offer any guidance on when its review would be complete, but he called the issue a "top priority" for the agency.

A Treasury spokeswoman did not respond to a request for comment.

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Wyden's request comes on the heels of another letter sent to the inspector general of the agency by Democratic Sen. Elizabeth Warren last week. Her letter, which was sent the day before the Senate prepared to vote on a sweeping tax reform plan, raised concerns about the promised analysis that has yet to be released by the agency.

The IG's office had begun looking into the matter before it received Warren's letter, according to Delmar.

In her letter, Warren also raised the possibility Mnuchin had "misled the public about the extent of the Treasury Department's analysis, "despite his repeated public assurances that an analysis existed and the tax plan would 'pay for itself.'"

Mnuchin has repeatedly pledged that more than 100 career staff members were "working around the clock on running scenarios" to show how the costs of the $1.5 trillion GOP proposal would be covered by economic growth. He even noted in September that an in-house analysis showed the bill would reduce the deficit by $1 trillion rather than increase it.

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At The Wall Street CEO Council conference in November, Mnuchin reaffirmed that Treasury had completed an analysis and pledged "complete transparency" in its accounting for the growth benefits of the tax plans.

The agency has yet to release anything.

Warren has asked the inspector general to find out whether Treasury's staff were directed to analyze the Republican tax proposal at all and if so, why the results weren't publicly released or given to Congress. She also asked the inspector to look into whether there was any political interference that would have impacted the outcome of the analysis or who participated in the efforts.