HARRISBURG — Prosecutors added a new perjury count and other criminal charges Thursday against Pennsylvania's attorney general, saying they found a signed document that contradicts her claims she never agreed to maintain secrecy of a grand jury investigation in 2009, before she took office.

The Montgomery County district attorney charged Kathleen Kane with felony perjury and two misdemeanors — false swearing and obstruction — based on a signed secrecy oath she signed shortly after taking office in early 2013.

Kane, the first woman and first Democrat elected attorney general in Pennsylvania, was previously charged with perjury, conspiracy and other offenses. Prosecutors said she leaked secret grand jury information about a 2009 investigation to a newspaper and then lied about it.

An affidavit filed by a county detective said Kane has repeatedly said she did not swear to keep secret the 2009 grand jury information about a former head of the NAACP in Philadelphia.

But the district attorney's office said her signed oath was recovered during a search of her Harrisburg offices on Sept. 17, contradicting her claims that no such document existed.

“Kane perpetuated this falsehood not just before (a) grand jury, but also in legal filings before the Pennsylvania Supreme Court and to the people of Pennsylvania through privately retained representatives,” wrote Montgomery County Detective Paul Michael Bradbury, who attached a photocopy of the one-paragraph oath to the affidavit.