Fire investigators say they have ruled out arson as the cause of the fire in the Gastineau Apartments building in downtown Juneau.

Capital City Fire/Rescue Fire Marshal Daniel Jager said burn patterns found in the fourth-story bedroom where the fire began indicated the blaze was not intentionally set. The patterns would have been different if an accelerant had been used, he said.

“It’s not intentional, I can tell you that,” Jager said in an interview at his office Friday afternoon.

All the residents of the South Franklin Street apartment complex were evacuated before the blaze consumed the top fourth-floor of the building. No life-threatening injuries or casualties were reported, although 50 residents were displaced.

Jager and a team of firefighters began investigating the fire’s cause on Tuesday. Its cause is still undetermined at this point, and there are multiple theories still in play, he said.

One of those theories is an unattended candle in the fourth-story bedroom. Jager on Friday described that theory as a “high possibility, or likely cause.”

Jager interviewed that tenant on Thursday and complimented the tenant for doing the right thing when he or she discovered the fire, which was to warn neighbors by knocking on their doors and to leave the area. The fire was too big for the tenant to extinguish when it was discovered, Jager said.

“The key there was to get out,” Jager said.

The tenant’s name was not released.

Based on the interview with the tenant, the fire department will not be recommending criminal charges to the District Attorney’s Office. Jager said this was not a case of gross negligence or intending to start a fire.

“I do strongly believe it was an accidental cause,” Jager said, though noting he still does not know what the cause is.

Jager said the fire department has also ruled out mechanical failure and appliance failure as the cause of the fire.

CCFR has interviewed the four or five people who lived on the top floor of the building. Some of the information they have received is conflicting, and the cause of the fire won’t be determined until CCFR conducts more interviews, Jager said.

While the on site investigation was completed earlier this week, the investigation is still ongoing. Jager said he did not know how long the investigation will take.

The fire department will also be waiting to make its finding until adjusters from the insurance company visit the site.

The fire department’s investigation, which is required by state statute, is independent of the insurance company’s investigation. But sometimes insurance companies have more resources at its disposal to confirm the cause of a fire, Jager said.

CCFR Chief Richard Etheridge, Jager and other CCFR personnel will be escorting the adjusters through the building on Monday.

• Contact reporter Emily Russo Miller at 523-2263 or at emily.miller@juneauempire.com.