But McGaffigan has never been a Dudley member, said Dingman, who is senior tutor of the House.

McGaffigan also told The Crimson she is pursuing a special concentration in “creative writing and literature,” and a member of her “Wit and Humor” section said McGaffigan had claimed to be pursuing such a concentration.

But staff in the committee on special concentrations, as well as in the English department and in the literature concentration, all said that McGaffigan is not and never has been a concentrator in their respective fields.

“She never even applied for a special concentration,” said Stephanie Macaris, the staff assistant for special concentrations.

McGaffigan, who said she was interested in performance studies, has performed with the Exhibitionists, a women’s performance art group in New York City. This past winter she performed a “chilling monologue” titled “Holy,” said Exhibitionists co-founder Jennifer Laskey.

The case against Leo Felton, 31, and Erica Chase, 22, was based largely on the testimony of McGaffigan, their one-time associate.

McGaffigan began to cooperate with the federal investigation leading to the Felton and Chase’s conviction, while under questioning by Secret Service agents the day after McGaffigan had removed 50 pounds of ammonium nitrate—a fertilizer used in making bombs—from Felton and Chase’s apartment.

A spokesperson for the U.S. attorney’s office would not say whether or not McGaffigan had been given immunity in exchange for her testimony.

“She has not been charged with anything at this point,” said Samantha Martin, another spokesperson for the office.

McGaffigan, who could not be reached for comment this week, is the third extension school student discovered posing as a Harvard undergraduate in the past three years.

—Staff writer Stephanie M. Skier can be reached at skier@fas.harvard.edu.