Hawaii’s statewide public library system is expected to be fully open to the public today after an “unspecified threat” closed dozens of branches to the public Monday, a spokesperson for the Office of the State Librarian said.

The closures made Hawaii’s libraries the latest library system to be targeted by threats during or close to national Banned Books Week, which was Sept. 18-24. Among the cities where threats have closed libraries temporarily this month are Salt Lake City; Fort Worth, Texas; Denver; and Nashville, Tenn.

An email received by Hawaii library system officials early Monday led them to decide to close to visitors, although library staff were permitted to continue working, said Mallory Fujitani, special assistant in the Office of the State Librarian. She declined to give details of the threat.

Hawaii has the only statewide public library system in the nation, with 51 libraries on six islands. About one-third of them already are closed routinely on Mondays. About half of the remaining libraries usually open at 9 or 9:30 a.m., the other half, around 11 a.m. or noon.

Shortly after noon on Monday, the Office of the State Librarian sent out a news release announcing that “all Hawaii State Public Library System locations are closed … out of an abundance of caution due to an unspecified threat. The library has been working with local law enforcement to determine when it is safe to reopen.”

A Honolulu Police Department spokesperson deferred to the state Department of Public Safety for comment, saying that agency was taking the lead.

“The Sheriff Division is aware of a vague threat made to the statewide public library system,” but it was not specific to any library location, said Toni Schwartz, public information officer for the Department of Public Safety. Sheriffs initiated a second- degree threatening case and were investigating, Schwartz said.

In some mainland cities, disagreements have reignited among parents, members of the public and library advocates over whether some books should be blocked from children, sparking vigorous arguments and protests.

In Utah, Salt Lake City Public Library received a bomb threat Sept. 12 that closed the library and surrounding businesses. Seventeen library branches in Fort Worth were evacuated Sept. 19 after multiple emails that contained bomb threats were received. All Denver libraries were closed and bookmobile stops canceled Sept. 21 “out of an abundance of caution” following an unspecified threat. In Nashville, an emailed bomb threat Sept. 22 led library officials there to close all branches for the remainder of the day.