Fire investigators have not ruled out any possible causes of a blaze that devoured a building at the University Laboratory School on Tuesday.

The fire engulfed the building that had held the school's music, theater and athletic programs. Damage to the building has been estimated at $6 million and at $500,000 for the contents. School officials, however, say they expect that to rise.

"We haven't eliminated any sources" of the fire, said Fire Capt. Jerry Spencer. "It was a big fire, and the investigator wants to make a thorough investigation. Sometimes these things take longer."

Police spokeswoman Michelle Yu said police also have not drawn any conclusions about the source of the blaze. An arson investigator was listening to 911 tapes yesterday, she said.

The building recently had undergone renovation and electrical work, according to Jim Manke, a spokesman for the University of Hawai'i.

The laboratory school, officially called the Educational Laboratory School, is operated by the UH College of Education's Curriculum, Research and Development Group. It is a state charter school.

Manke said the floors in the building had been varnished the week before the blaze, but all flammable materials had been removed from the building at the completion of the job.

He also said that an underground electrical cable that had supplied power to the building had stopped functioning after heavy rains in March. The power company brought a line down from a transformer and pole along Metcalf Street as a temporary fix, he said.

Jose Dizon, a Hawaiian Electric Co. spokesman, said power to that line was cut during the blaze at the fire department's request, a standard procedure during a fire. He said he knew of no evidence that there had been any malfunction of the line.

Manke said university officials are still working to calculate the actual value of the contents of the building.

The loss included musical instruments for the entire orchestra, he said, and officials value them at roughly $50,000. No student had left personal instruments in the building, he said.

Costumes from the theater workroom were burned, as was equipment in the weight room, athletic uniforms for all the teams and athletic trophies kept in the building.

One wing of the L-shaped building was used for university offices, and contained "countless computers," Manke said.

Because of the ongoing investigation, university officials have been unable to access the debris to determine what, if anything, can be salvaged, he said.

Reach Karen Blakeman at kblakeman@honoluluadvertiser.com.