HILO, Hawai'i — Big Island police have determined a fire that did an estimated $1.5 million damage to Waiakea High School's administration building was deliberately set.

Police Capt. Chadwick Fukui said there is evidence an accelerant was used to start the fire in the registrar's area of the administration building, but more tests are needed to determine if gasoline or some other flammable chemical was used.

Fukui declined to say whether there were signs of forced entry into the building.

The fire at about 1:07 a.m. Tuesday was the third fire deliberately set on the Waiakea campus in the past eight weeks. The other two fires on Feb. 15 and April 5 did only minor damage to two portable classroom buildings.

The school has not held classes since Tuesday's fire in Building A, but Waiakea Principal Patricia Nekoba said the school's 1,300 students will return Monday.

Staff worked during the past week to move offices, with the main office and student services office set up in the school library, and other offices from the administration building moved elsewhere on campus, Nekoba said.

School will open with a morning assembly to brief the students, and report cards will be distributed during first period, she said. Report cards were originally scheduled to be distributed Tuesday.

Big Island police have asked for the public's help in identifying who set the blaze, and Fukui said police have been following up on tips phoned in by residents.

Anyone with information about the fire is asked to call Detective Tom Poy at 961-2383 or the police nonemergency number at 935-3311.

Tipsters who prefer anonymity may call CrimeStoppers at 961-8300 in Hilo or 329-8181 in Kona. All CrimeStoppers information is kept strictly confidential.

Reach Kevin Dayton at kdayton@honoluluadvertiser.com.