Thieves using credit cards stolen at Harvard have illegally charged more than $50,000 worth of merchandise, private investigators said yesterday.

The investigators said that the thefts, which have occured in the last several months, appear to be the work of an organized gang.

All but one of the many thefts have taken place at Blodgett Pool. Richard J. D' Amico, the chief investigator on the case said yesterday. He said there appears to be a pattern to where the stolen cards are used, and investigators are trying to link the thefts to a known cred't-card stealing ring in New Hampshire.

Possible Indictments

D'Amico said he hoped to have gathered enough evidence by the end of the year to approach a federal grand jury and request in dictments in January.

University Police Capt Jack Morse said theft from the pool has been an ongoing problem Most thefts occur from unattended lockers when people are swimming, he said.

Morse said that be is aware of the investigation but the Harvard department is not actively participating.

Behind the front desk at Blodgett are photographs of suspected card thieves Door checkers are supposed to watch for the people pictured and not admit them to the pool area a door checker working yesterday afternoon who asked not to be identified, said.

D'Amico said the stolen cards were usually used to purchase theater or plane tickets and other merchandise which is then resold Credit cards stolen from Harvard have turned up all over New England and as far away as Philadelphia, he added.

D'Amico and his staff of two investigators work for First Data Resources, a private company which has contracts with area banks and the national credit cards Mastercard and Visa. He is responsible for investigating all credit card fraud in New England and New York.

Mail Fraud

United States Postal Inspectors have recently entered the case because the thieves have used stolen cards to purchase mail order merchandise Postal inspectors working on the case could not be reached for comment yesterday.

The First Data Resources investigators last week approached the U.S. Attorney in Boston to discuss the case and ask that handwritting samples of people associated with the New Hampshire card ring be subpoenaed D'Amico said they want to compare the handwriting with signatures on forged receipts associated with cards stolen from Harvard.

D'Amico refused to name any specific suspects in the case but said You might be surprised there's some pretty prominent people involved.

At Harvard

Dean of Students Archie C Epps III said he had not heard of the investigation but that it would be the first of its kind at the College.

He added, however, that theft is a common occurence at Harvard and many students are not sufficiently aware of the problem.

Most people, "are unaware of the fact that they've got the problem. People have just got to take care of their cards." D'Amico said.