NoBo library branch was closed and the alarm was going off. Bookworms were inside anyway.

The NoBo branch of the Boulder Public Library is closed Wednesday. That didn’t stop some bookworms from getting inside while the alarm was going off.

Three of the library system’s branches, including NoBo, are closed until noon Wednesday for staff training, according to a notice on the system’s website.

But customers were inside the NoBo branch, at 4500 13th St., as of about 9:20 a.m., with no staff or security personnel present, according to Boulder Police Department Sgt. Steve Saber.

Neither Boulder police nor the library knows how people initially got inside.

Facilities personnel were en route to the NoBo Library, a library specialist said.

This is a developing story and may be updated.