The Manhattan District Attorney this week subpoenaed the trading records of a small New York brokerage firm as part of a probe into whether the firm was used by organized crime to manipulate stocks and defraud investors, two people with knowledge of the situation say.

The firm,

Couch & Co.

, on Dec. 1 began filing to terminate its state securities registration with the

National Association of Securities Dealers

, which one of the people familiar with the situation said is also looking into the firm's activities. An NASD spokeswoman declined to comment or provide names of the firm's principals.

Thomas M. Couch, who said he now owns a minority interest in the firm, said Friday the company had responded to a subpoena from the district attorney's office. "They're looking into trading in certain stocks. We've given them everything," Couch said, adding that he's not aware whether finding an organized crime influence is at the center of the inquiry. Couch declined to name the stocks the district attorney is examining.

A man identifying himself as Anthony Radicone, a Couch & Co. employee in New York, declined to comment on the inquiry or name the firm's majority owners. He referred calls to an attorney, Ronald Brescher, who was out of the office and didn't return calls seeking comment Friday.

The two people familiar with the situation said the D.A.'s subpoena was made out for an inquiry of "John Doe" and not to any particular Couch & Co. executive or employee, which could mean authorities may not want to tip their hand regarding the targets of their work.

Citing policy, the D.A.'s office declined to comment on the subpoena.

Since the 1990s bull market has been in full swing, organized crime figures have increasingly used brokerage operations to artificially inflate the prices of securities they hold, then sell them into the rising market. In an October indictment of top members of the DeCavalcante crime family of New Jersey, Mary Jo White, U.S. attorney for the

Southern District of New York

, called the family's involvement in securities fraud "the new face of organized crime."

In June, the

FBI

wrapped up an investigation of securities fraud by arresting more than 100 suspects, many with ties to the

Colombo

and

Bonanno

organized crime families.

Couch & Co. has no known connection to any of those cases.

Couch & Co. was previously registered as a Houston-based firm under the name

Thomas M. Couch Inc.

, but according to current NASD records is now based in Manhattan. Thomas Couch, who still works out of Houston, said the firm's headquarters moved to Manhattan in June. "Most of the company's business was conducted in New York," he said.

Couch said that while he did file some regulatory reports, he never had any supervisory role at the New York office or dealt in any of the stocks that are being examined.