Saying he had been motivated in part by The Times’s findings, New York’s finance commissioner, Jacques Jiha, began last spring to require that all members of LLCs be disclosed to the city for tax auditing purposes when deeds were transferred. Mr. Jiha said that wealthy residents might be able to use a “veil of secrecy” to evade city taxes by claiming to live elsewhere. While the new rules went beyond what many jurisdictions require, experts called them imperfect, because some LLC members are nominees, meaning the true owners remain hidden.

Mayor Bill de Blasio’s administration is sponsoring legislation in Albany intended to prevent deed theft. The bill’s provisions include a requirement that notaries public be fingerprinted. But the city recently removed a provision that would compel additional disclosure of LLC ownership in real estate transactions. While real estate interests had objected to the requirement, Sonia Alleyne, a spokeswoman for the Finance Department, said that was not why it was dropped. Instead, she said, city officials believed the new requirements imposed by Mr. Jiha had begun to work.

At the same time, investigators have been working to crack down on fraudulent deed transfers. Beyond the 120 cases under investigation, the Finance Department is aware of another 167 cases that appear suspicious, according to Joseph Fucito, the New York sheriff, the agency that investigates allegations of deed fraud. Indictments have been handed up in all five boroughs, with 16 arrests since July 2014.

But lawyers who have represented deed fraud victims said the sheer volume of such cases, which some estimate to be in the thousands, and the difficulty of tracking down the perpetrators, had overwhelmed law enforcement agencies.

Even so, in May, Preet Bharara, the United States attorney in Manhattan, announced the indictment of three men accused of tricking people into signing over properties in the Bronx, Brooklyn and Queens.

The men’s company, Homeowner Assistance Services of New York, relied on telemarketers to promote their alleged scheme. Among those who received a call were Roy and Iris Jones.

The Purloined Property

Mr. and Ms. Jones have owned a multiunit building on Fulton Street in Brooklyn since 1999. An appraisal they commissioned put its value at $2.8 million. The couple used to operate an upholstery shop in the building. Since closing the shop, they have rented the property to tenants.