Wednesday, March 31, 2010 | 1:06 p.m.
CARSON CITY - Nevada Capitol police installed tighter security measures this morning after law enforcement officials received a letter from an extremist group telling Gov. Jim Gibbons to resign.
All entrances to the building have been closed except the main entry, and a metal detector and X-ray machine have been set up at that entrance to screen visitors and packages.
"We're using every precaution," said Lynn Hettrick, deputy chief of staff to Gibbons.
Capitol police received a threatening letter Monday from a group that Hettrick said he could not identify. Hettrick said the FBI issued a warning that letters would be sent to governor's in all 50 states, telling them to resign their posts and swear a new oath of office.
Hettrick said that the group threatened to "commandeer" state offices, though it also said it was a non-violent movement.
Five of the six state constitutional officers work in the Capitol. A steady stream of tourists are usually taking self-guided tours of the historic building.
Hettrick said the group was affiliated with the "sovereign citizens" movement, which the Anti-Defamation League describes as a "loosely organized collection of groups and individuals who have adopted a right-wing anarchist ideology."
The Anti-Defamation League says Terry Nichols, accomplice to Oklahoma City Federal Building bomber Timothy McVeigh, was part of this group.