SALT LAKE CITY– Investigators have closed the books on the massive four-alarm fire that destroyed a Sugar House apartment building under construction last October.

In a report obtained by KSL, fire investigators called the official cause of the fire “undetermined.”

The report does mention two possible causes of the fire: temporary heaters or electrical boxes, combined with nearby fuel sources and oxygen from partially opened windows and doors.

“The reports talk about numerous other things such as the spider boxes, the heaters, and arson as still being suspicious and potential causes of the fire. But we did not find any evidence that could directly link the cause to those things,” said Captain Shaun Mumedy with the Salt Lake City Fire Department.

Mumedy told KSL NewsRadio the fire burned for almost a week.

“The longer something burns the potential for evidence to be ruined goes up,” he said.

The fire initially displaced dozens of people living in neighboring apartments and shut down nearby businesses for weeks.

Investigators estimated the fire caused $59 million in damages, and that’s only for the Sugar Alley Apartment building that burned down.

Mumedy said the cause will likely stay undetermined since authorities have been combing through evidence from the Sugar House fire for months.

“Unless someone comes forward with some new evidence … this is probably where it’s going to stay,” Mumedy said.