The four-alarm blaze erupted at around 6:30 p.m. Sunday night at the construction site of an apartment complex at 550 E. 500 South.
Salt Lake City Police Lt. Josh Scharmin said a man was found at the scene of the fire wearing a firefighter uniform. When Salt Lake City Fire personnel discovered he was not among their ranks, the man was taken into custody. Scharmin said the man was detained and was being questioned Sunday night.
Salt Lake City Fire officials said the man is in his 20s, and fire investigators detained him after giving false information to law enforcement.
Salt Lake City Fire spokesman Jasen Asay said the fire tore through an apartment building that had been under construction with no utilities hooked up. According to fire officials, the building's construction company said there was no work being done on the building Sunday and there was not heating or electronics in the building.
The flames grew quickly because of the amount of exposed wood on the unoccupied construction site. Asay said firefighters had to evacuate all the buildings in the area near the fire, including a Smith's Marketplace nearby.
At its peak, the flames from the downtown fire could be seen from miles away.
According to a staff report from Salt Lake City Planning and Zoning Division, the property where the fire started is owned by Strategic Capital Group. In May 2013, the report recommended that the city approve the building of a subdivision called the Newhouse Apartments.