The insurance program, which also backs the mortgages of just over 1,000 assisted living facilities, is a pillar of the country’s elder-care system, keeping borrowing costs low for financially struggling care centers. About 15 percent of the country’s nursing homes are supported by the program, compared with about 5 percent a quarter-century ago.

The Rosewood default prompted the HUD inspector general to issue subpoenas seeking financial records for the operation of the Rosewood facilities, according to court filings. Lawyers for some investors in the nursing homes said the F.B.I. was investigating, along with the Securities and Exchange Commission.

In the case of Rosewood, the ownership group led by Zvi Feiner, a rabbi from Skokie, Ill., defaulted last August on $146 million in mortgages for the facilities in Illinois and St. Louis after years of failing to pay the lenders and vendors. Last week, a federal administrative law judge approved a settlement requiring Mr. Feiner to pay $965,678 for failing to file three years of audited financial reports required under the mortgage program.

HUD, in addition to appointing a receiver to manage the facilities, has paid about $18 million to operate the nursing homes while it sought a buyer. Last month, lawyers for the government told the federal judge presiding over the receivership that it had selected a firm to buy the facilities. It did not identify the winning bid because the sale had not been completed. A department spokesman also declined to identify the buyer.

Greystone, a large real estate lending and management firm that had been servicing the Rosewood mortgages when the company defaulted, confirmed through a spokeswoman that it had submitted a bid for the Rosewood properties. But Greystone, one of the nation’s largest lenders under the nursing home mortgage guarantee program, would not say if HUD had selected it.