The FBI is investigating the possible theft of software developed by the nation's leading maker of electronic voting equipment, said a former Maryland legislator who, this week, received three computer disks that apparently contain key portions of programs created by Diebold Election Systems.

Cheryl C. Kagan, a former Democratic delegate who has long questioned the security of electronic voting systems, said the disks were delivered anonymously to her office in Olney on Tuesday and that the FBI contacted her Thursday. The package contained an unsigned letter critical of Maryland State Board of Elections Administrator Linda H. Lamone that said the disks were "right from SBE" and had been "accidentally picked up".

Lamone's deputy, Ross Goldstein, said "they were not our disks," but he acknowledged that the software was used in Maryland in the 2004 elections. Diebold said in a statement last night that it had never created or received the disks.