Sen. Gary Peters of Michigan is pressing the U.S. Department of Housing and Urban Development to explain how it decided to spend more than $31,000 for a custom-made hardwood dining set for Secretary Ben Carson’s office.

Peters, the ranking Democrat on the Senate’s Federal Spending Oversight and Emergency Management Subcommittee, wrote to HUD with two colleagues this week to express dismay over a “troubling pattern” of senior administration officials “wasting taxpayer money on extravagant goods and services.”

The senators are also probing allegations that the department retaliated against HUD employee Helen Foster, who says she was demoted after she spoke up and tried to prevent the expenditures.

Under federal law, Congress is supposed to be notified when an agency spends over $5,000 on furnishing or redecorating the executive suite of a department head.

“Our most fundamental responsibility as public servants is to use tax dollars prudently and efficiently, and approving the purchase of expensive furniture at a cost that exceeds the median wage American workers take home in a year is an inappropriate use of taxpayer funds,” wrote Peters, who was joined by Democratic Sens. Elizabeth Warren of Massachusetts and and Catherine Cortez Masto of Nevada.

HUD initially defended the purchase but later indicated that Carson, a Detroit native, directed staff to cancel the order after the House Committee on Oversight and Government Reform announced an investigation into the matter.

“Secretary Carson was surprised to learn a $31,000 dining room set had been ordered,” spokesman Raffi Williams said Tuesday by email.

“At his direction, the order was canceled and the funding will be returned to the Treasury. He is fully cooperating with the Committee’s request.”

Peters’ letter asks HUD for copies of all contracts and records and communications among HUD employees related to ordering furnishings or other items to redecorate Carson’s office suites, as well as communications regarding Foster’s involvement in approving the purchases.

Specifically requested are records associated with the Dec. 21 purchase of the $31,561 dining set from Sebree and Associates LLC, and how much of the purchase cost HUD expects to recover once the order is canceled.

The senators also requested the names of non-HUD individuals who played a role in selecting, procuring or ordering the furniture, and when Carson first became aware that HUD intended to purchase the furniture set and his role in its selection.

Peters also wants to know HUD’s justification for the September purchase of $165,000 worth of lounge furniture for its headquarters.

In a Facebook post on Monday, Carson thanked supporters as the “character attacks on us have increased in an attempt to claim that a scandal has occurred.”

Carson said the secretary’s dining room is used for business luncheons but the furniture is 30 to 50 years old, “very worn” and “characterized as unsafe.”

“I did not request new furniture, but asked if it could be remediated. I was subsequently told that it was beyond repair and needed to be replaced,” Carson wrote.

He says he briefly reviewed furniture catalogs and was shocked by the cost, but was told that used furniture was not an option because HUD’S acquisition process “did not allow for that.”

“We were told there was a $25,000 budget that had to be used by a certain time or it would be lost,” Carson wrote.

“I made it clear that I was not happy about the prices being charged and that my preference would be to find something more reasonable.

“I left this matter alone to concentrate on much bigger issues. I was as surprised as anyone to find out that a $31,000 dining set had been ordered. I have requested that the order be canceled. We will find another solution for the furniture replacement.”