The mysterious cause of the Cape Horn Fire, which burned 1,326 acres and destroyed homes and timberland last summer near Bayview, remains a mystery.

According to a report released Friday by the Idaho Department of Lands, the year-long probe isn’t over.

"We believe that this is a human-caused fire," David Groeschl, IDL deputy director, said during a press conference Friday. "But we cannot — at least right now — we have not been able to determine the actual or exact cause."

If officials do, however, somebody’s going to get a $5.6 million surprise.

“If the exact cause is determined and the responsible party is identified, then we would submit a bill to cover the cost for the suppression efforts on this fire,” Groeschl said.

Four investigators determined the point of origin was within 20 feet of a beach that was occupied by two campers at the time. A white material found at the point of origin is believed to be the ignition source, described in the report to be made of layers similar to cardboard or a wad from a shotgun shell. It appeared to have originally been round.

The investigation initially led investigators to believe it was possible the material was from a marine flare fired by the campers, and that may have started the fire. But after three labs — Idaho State Police, FBI and a private lab — tested the material, investigators determined neither the white object nor the underlying soil sample contained any chemical residue or material consistent with a marine flare, Groeschl said.

The fire started shortly after noon last July 5. It ended up destroying nine homes and five other structures, as well as damaging another home. The area encompassed by the fire included U.S. Forest Service land, land owned by IDL, Stimson land and privately owned land.

Lisa Gibson and Kim Cannon, whom Groeschl said are "from the area," boated to the small beach located north of Cape Horn July 3 to camp and watch the Fourth of July fireworks show in Bayview. After making it to the show and back to the camp, an early morning windstorm July 5 swamped their boat and left the two women stranded, the report states. Gibson contacted the Bonner County Sheriff's Office, told them where they were and said they were stranded, but there was no need for immediate rescue because they were safe and had food and water.

Around the same time as she placed the call, the women fired two flares. One was reported to be a dud that blew back to shore. That afternoon, Gibson smelled and saw the smoke just above their camp and called 911 again, according to the report. The report shows photos of the "V" pattern of the fire as a "very strong northerly wind" pushed it up the hill.

Witnesses reported seeing a flare around 4 a.m. Bob Helmer, IDL's lead investigator, said the women did not immediately report firing the flares when interviewed by investigators, but later offered the information and admitted to destroying the flare gun.

"We didn't know about the flares when we started asking them questions," Helmer said.

Although the women did not initially offer the information, Helmer said they did cooperate with investigators. When asked by investigators why she fired the flares, Gibson reportedly said she wanted to "see what it would do." He also said the destruction of the flare gun raised some questions.

Early reports also indicated the women may have had a campfire because several items in the camp were burned, including a foam pad and a cooler. Groeschl said that was caused by embers falling from the fire above and there was no evidence of a campfire on the beach.

Groeschl said there are no ongoing tests being done on the white material believed to be the ignition source, but the conversation will continue with the lab to determine if other tests can be done. He said the flare has not been completely ruled out, although the lab results indicate it was not the source. Helmer said devices such as fireworks or flares would leave residue in the soil and could not be completely destroyed by the fire.

Helmer said people coming forward with information down the road can often help in those cases, and IDL is asking anyone who may have information to come forward.

Groeschl said the investigators are required to determine whether someone "willfully or negligently" started a fire. Willfully starting a fire would typically be considered arson, which is not the case with the Cape Horn Fire. To determine negligence, which is believed to be the case, they have to be able to determine the cause, Groeschl said. If the flare had been found to be the ignition source, Groeschl said the women would have been negligent for firing it because, as Gibson said, they weren’t in distress; they just wanted to "see what it would do."