At least 18 cases of arson have occurred in the library since it reopened 10 days ago, following five months of work to repair serious damage from the flood that swept through Manoa Valley last October.

The fires were small but have damaged books, newspapers and furniture, and are a serious safety threat because fire could quickly spread among the library's materials, officials said.

The building's fire alarm system remains inoperable due to flood damage, and an improvised system that includes manually operated aerosol horns has been set up.

The fires prompted officials to quadruple the number of security guards deployed inside the library, and to install a video surveillance system. Police are investigating the incidents, and library visitors are now required to show identification and sign their names before entering.

"It's kind of a pain in the butt to sign in, but I understand why," Peters said. "Hopefully, the security and everything will put a stop to it."

The fires began a few days after the library reopened, and on some days several were set, UH spokesman Jim Manke said. Most just simply burned out, and none was serious enough to sound a fire alarm or require an evacuation, he said.

"It's unfortunate that after all the work that went into reopening the library, we have to deal with this," Manke said. "But we're taking this very seriously."

No library materials were completely destroyed, but some damaged books and newspapers have been set aside as evidence. Fires were lit on the library's second, third and fourth floors, Manke said.

Smoking is not allowed in the library, and there is no legitimate reason for anyone to bring matches or a lighter inside, he said. Library visitors and employees should immediately report any suspicious activity to security guards, he said.

Honolulu Police Department Detective Tasman McKee said it appears that the fires were set randomly, and did not target any specific library collection or materials. It's unclear whether the fires were set by one person or several, or whether they are intended to convey any message, he said.

Whoever is responsible for the fires could face felony arson charges, McKee said.

No similar fires have been reported at the university's Sinclair Library or other facilities, Manke said.

The fires have deeply angered librarians and students.

"It's upsetting to everybody, obviously," said Allen Riedy, head of Hamilton Library's Asian Collection, where one of the fires damaged a stack of newspapers. "We don't quite understand what this person is up to. The fires have been small, but there have been a lot of them."

Librarian Alice Mak, a specialist on material about the Philippines, said she was disgusted by the incidents.

"I'm appalled that anyone would want to do something like that, risking lives and materials," she said.

Monica Ghosh, a librarian in the South Asian section, also was outraged.

"It just seems bizarre and disturbing," she said. "It's such a risk to both people and the materials. Whenever anybody violates the material at the library, it's something we find appalling."

Between 2,000 and 3,000 people use the library each day, and it is expected to be very busy over the next four weeks as students study for final exams.

"It's definitely a shame that the library has to go through this, especially after the flood," said graduate student Heather McRae. "Arson's a serious thing, but especially when you have a fire alarm system that's not quite back on track."

Manke said the improvised alarm system has been approved by university safety officials. Each library visitor is handed an instruction sheet that warns of the situation and explains alarm and evacuation procedures. Signs also warn of the arson incidents.

Full repairs to the library's alarm system are expected to take one year, library special assistant Jean Ehrhorn said.