The longtime companion of notorious fugitive James "Whitey" Bulger pleaded not guilty in Boston Thursday to charges she harbored and concealed him, said a spokeswoman for the U.S. attorney for the District of Massachusetts.

Catherine E. Greig, 60, who is being held without bail, allegedly assisted Bulger from January 1995 until June, when the pair was arrested in California, the U.S. attorney's office said in a statement last week.

"It is alleged that Greig conspired to take steps to prevent Bulger's discovery and arrest, after knowledge of the fact that a warrant had been issued for his apprehension," the office said.

Greig's attorney, Kevin Reddington, did not immediately return calls for comment Thursday.