Update, May 23 6:15 p.m.
Fire investigators have determined the blaze started accidentally due to roofing operations, officials said.
"A damage estimate has not been created due to the unknown amount of smoke and water damage throughout the structure," the Manhattan Fire Department said in a release. "Assistance from Kansas State University will be needed to determine an accurate loss amount once an assessment of the building and contents is complete."
The building has been turned back over to the university, but it remains closed, the release said.
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Hale Library at Kansas State University will be closed after a fire broke out on the roof Tuesday afternoon.
The blaze was reported at 4:10 p.m. after smoke began to fill the library's fourth floor. At 5:30 p.m., seven trucks from the Manhattan Fire Department had responded, and smoke was still billowing from the building, according to the university.
It was declared a third alarm fire before being contained more than two hours after the smoke was reported, the Manhattan Fire Department said.
The fire was in the northwest part of the original Farrell Library portion of Hale Library, "in an area containing several large air handling units."
It "proved very difficult for firefighters to gain access to extinguish the fire. Damage estimates are not available at this time. Fire damage was limited to a portion of the roof, with extensive water and smoke damage throughout the structure," the department said.
No injuries were reported. Crews from the Riley County Emergency Medical Services, Fort Riley and Blue Township also responded.
Investigators from the Bureau of Alcohol, Tobacco, Firearms and Explosives, the Kansas Office of the State Fire Marshal and the Manhattan Fire Department will investigate the cause.
The university's data center is temporarily down and staff was asked on Twitter not to go to the library on Wednesday.
The library was built in the 1920s and opened in 1927. It was remodeled in the 1990s. Hale Library has more than 400,000 square feet of space and has more than 2 million books in its collection.