The Oregon State Police say the number of courthouses that received bomb threats Monday has increased to 28.
Authorities initially reported that 17 county courthouses were targeted in what apparently was a coordinated effort.
State Police Lt. Gregg Hastings says the Oregon Judicial Department did a complete assessment on Tuesday.
Twenty-two of the 28 courthouses were evacuated, along with a state office building in Salem that houses the State Police headquarters. Hastings says it's unclear whether more than one caller was involved.
He says state investigators will gather information from each county that received a threat, but it's unclear why certain counties were targeted.
All Oregon counties were targeted except Clackamas, Columbia, Coos, Douglas, Harney, Hood River, Josephine and Linn. Similar threats were reported this month in Washington and Nebraska.