The Nashville Public Library system was forced to close its branches Thursday after receiving an anonymous bomb threat via email the latest in a line of similar scares across the country recently.

Police determined that the message likely came from outside of Tennessee and was not credible, according to NewsChannel 5 in Nashville. But library management opted to temporarily shutter its locations after receiving the email, which hadnt targeted a specific branch.

This is so common now. This is domestic terrorism, Nashville Councilwoman Ginny Welsch told NewsChannel 5. This is trying to make us all afraid, and a library is really the perfect target for this kind of stuff because it is a place of knowledge and information and history.

Libraries nationwide have likewise received threats in past weeks, which tend to arrive over the internet from somewhere other than the targeted location, though its unknown if they are linked.

Earlier this month, Salt Lake City Public Library employees received a bomb threat that didnt mention a specific branch, according to ABC4 in Utah . A staff member found an unattended bag near one building, but local law enforcement found no explosives in a search and said the public was not at risk.

More threats came this week.

On Monday, a Fort Worth Public Library employee in Texas received three emails indicating a bomb threat, according to the Fort Worth Star-Telegram . A library spokesperson said the messages didnt contain any explanation for the threat, but 17 branches were evacuated and closed early. Law enforcement determined that the emails originated from outside of the United States and werent credible. The libraries reopened the following day.

Then the Denver Public Library shuttered its branches Wednesday after receiving an unspecified threat overnight, reported 9NEWS in the Colorado capital. A nearby high school also closed that day after a threat circulated on social media, according to local outlet 11 News .

Hoax threats appear to be an escalation of a conservative culture war that has taken off over the past year, with right-wing groups focusing their ire on public libraries for hosting events and books with LGBTQ or racial justice themes.

Extremists have protested drag queen story hours, calling the family-friendly events a haven for pedophiles. A record number of books are facing bans. Religious organizations have mounted campaigns to block people from reading books about LGBTQ communities, and library employees have left their jobs amid harassment.

Then there are the conservative parents determined to remove books that they dont like from the facilities. A town in Michigan voted to defund its own library because it had books with LGBTQ characters, which some residents theorized were actually pornography or a stepping stone to child abuse.

And many Republican officials have not been shy about joining the faux panic. Last year, Texas state Rep. Matt Krause circulated a list of hundreds of books that he suggested school districts should review. Officials in Llano County shut down the public library system despite it not being a part of the school system to check the titles and remove any deemed questionable. Residents have since filed a lawsuit.

The source of the bomb threats and messages targeting libraries is still a mystery. But their effect is similar to that of the other campaigns against the facilities this year: sowing chaos and confusion while harassing staffers and closing down the institutions, even if temporarily.