WASHINGTON — The Treasury Department's internal watchdog has opened an inquiry into the department's Opportunity Zone program after a request in October from three Democratic members of Congress, Acting Treasury Inspector General Richard Delmar said.

Jared Kushner, President Donald Trump's son-in-law and senior adviser, in November 2018. Saul Loeb / AFP/Getty Images file

In late 2018, NBC News reported that Richard LeFrak, a friend of Trump's, and the family interests of Jared Kushner, Trump's son-in-law and senior adviser, among others, could benefit from possible projects in designated opportunity zones. The New York Times published a similar report last year.

The program, which Sens. Cory Booker, D-N.J., and Tim Scott, R-S.C., added to the 2017 tax bill, was meant to spur growth in underserved areas, and it prompted the designation of 8,800 lower-income census tracts as opportunity zones where investors could reap significant tax benefits.

Last October, Booker and Democratic Reps. Ron Kind of Wisconsin and Emanuel Cleaver of Missouri sent a letter to the Treasury Department's Office of Inspector General asking how the zones were chosen.

"The underlying legislation, the Investing in Opportunity Act, was intended to support the growth and revitalization of our nation's most economically underserved communities," the letter said. "It was not the intent of Congress for this tax incentive to be used to enrich political supporters or personal friends of senior administration officials, as recent reports indicate."

Delmar said in an interview that he expects his office's work to be completed by early spring.

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NBC News and other news organizations have reported that the program, which was created to help lower-income communities, has been benefiting higher-income areas.

Opportunity zone investments so far have reached more than $7 billion, according to the accounting firm Novogradac, which has been tracking the investments.