A former government contractor accused of stealing reams of top secret government documents has pleaded not guilty.

Harold T. Martin was arraigned in U.S. District Court in Baltimore on Tuesday.

A federal grand jury indicted Martin last week on 20 counts of willful retention of national defense information. Each count carries a possible 10-year prison term.

Martin, who worked for seven private firms, is accused of stealing top secret and classified documents from the National Security Agency and other government agencies over a span of 20 years, and keeping them in his home, car and an outdoor shed.

Prosecutors on Tuesday said they believe a trial would take between three and four weeks.

(AP)