NEW YORK (Reuters) - A U.S. grand jury formalized criminal charges on Wednesday against two former computer programmers at swindler Bernard Madoff’s firm, alleging they conspired with others to falsify investor records using a special program.

The two men, Jerome O’Hara, 47, and George Perez, 44, were originally charged last November 13 for their purported role in the multibillion dollar, decades-long fraud against thousands of investors at Bernard L. Madoff Investment Securities LLC in New York.

O’Hara’s lawyer, Gordon Mehler, said his client “intends to plead not guilty and even though it’s been more than four months (since his arrest), he is still presumed innocent.”

An attorney for Perez could not immediately be reached to comment.

If convicted, they each face maximum possible prison sentences of 30 years and millions of dollars in fines. Madoff, 71, is serving a 150-year term after pleading guilty a year ago of masterminding the huge fraud.

He was arrested in December 2008 after confessing to his sons and the FBI to running an epic Ponzi scheme that prosecutors said amounted to as much as $65 billion. A Ponzi scheme is one in which early investors are paid with the money of new clients. The Madoff firm made few actual trades in securities, investigators said.

O’Hara and Perez “were indicted today by a federal grand jury in Manhattan on charges of conspiracy, falsifying records of a broker-dealer and falsifying records of an investment adviser,” a statement by Manhattan U.S. Attorney Preet Bharara said.

O’Hara and Perez, employed at the firm from 1990 and 1991, respectively, were primarily responsible for developing and maintaining computer programs in the investment advisory unit at the center of the fraud.

Many of the programs were run on an IBM server known as “House 17,” according to court documents. Prosecutors said the men took hush money to help keep the fraud going and designed codes to make up fake trade blotters and phantom records.

U.S. prosecutors said the two men worked under the supervision of Madoff and his top aide, Frank DiPascali, to deceive the U.S. Securities and Exchange Commission and a European accounting firm. DiPascali is cooperating with prosecutors, who said his information led to the arrests of the programmers and the now defunct firm’s outside accountant.

DiPascali pleaded guilty to 10 criminal charges last August and is awaiting sentencing. The Madoff firm’s outside accountant, David Friehling, is also awaiting sentencing after pleading guilty. One other former Madoff employee, Daniel Bonventre, has been criminally charged so far in the investigation.

The case is USA v O’Hara et al, U.S. District Court for the Southern District of New York, No. 09-mj-02484.