(CNN) -- Courthouses and other government buildings in 30 Tennessee counties received bomb threats Tuesday, a state official said, making it the fifth state this month to see a similar round of false alarms.
No explosive devices had been found in any of the counties where threats were called in, said Dalya Qualls, a spokeswoman for the state's Department of Homeland Security.
Qualls said county courthouses, as well as federal and state buildings, received threats on Tuesday.
Tennessee's bomb scares came eight days after similar threats were made to 28 courthouses and a state office building in Oregon and within a month of similar incidents around Nebraska and Washington, according to Oregon state police.
Qualls said Tennessee Highway Patrol officers are assisting local authorities as needed, but the threats were still being investigated at the local level Tuesday evening.
CNN's Joe Sutton and Jennifer Hauser contributed to this report.