MILLCREEK, Utah (ABC4) – In mid-June, bright orange flames and billowing black smoke rose into the air as a three-alarm fire tore through a Millcreek construction site.

Over 60 firefighters from six different agencies responded to the structure fire along Highland Drive, which not only destroyed the construction site, but numerous nearby businesses.

SLIDESHOW: Photos of the Millcreek Fire

Investigators from the U.S. Department of Justice and the Bureau of Alcohol, Tabacco, Firearms, and Explosives assisted in the investigation.

Now, more than a month later, Unified Fire Authority tells ABC4 they do not believe the massive fire was caused by arson.

While they have ruled arson out, authorities say the cause of the Millcreek fire remains undetermined.

In the days after the Millcreek fire, multiple arson suspects were arrested across Utah for separate fires.

A 37-year-old man was arrested in connection with a three-alarm structure fire in Sugar House. He was accused of setting fire to a multi-unit office building by placing gasoline from a glass container on a wall of the building, then igniting the gasoline. Arresting documents show he was also violating a stalking injunction that an employee of the office building filed against him.

In Murray, a 27-year-old man was taken into custody after allegedly setting fire to an apartment building.

A woman was arrested after authorities say she started a brush fire in Layton.

In early July, authorities in Millcreek took a 23-year-old man into custody for allegedly starting an apartment on fire and damaging two cars.

Another man in Ogden was arrested after being accused of starting an apartment complex on fire. Authorities say he had recently been evicted.