Firefighters responded about 1:50 a.m. to the 200 block of S. Los Angeles Street, near 3rd Street, and found flames shooting from the building, according to Nicholas Prange of the Los Angeles Fire Department. A homeless encampment directly across the street was also on fire when crews arrived.
Video from the scene showed flames coming out of one side of the building and what sounded like several small, firecracker-like explosions and thick, black smoke pouring out of another side of the structure.
An official cause of the fire has not been determined, but LAFD Captain Erik Scott said cartridges being sold for commercial use by a smoke shop on the first floor of the building could be the cause of those small explosions.
"We're determining exactly what those cartridges are, what was inside and what (was) the quantity, but that will take time," he said.
The building, which housed several businesses, including two smoke shops, a luggage business and gift shop, was declared unsafe to enter.
Artist Nicholas Naughton had his studio in the building and now his artwork from six years of his career is gone forever.
""It kind of feels like a part of me is gone," he said.
Hedy Torres, another artist who worked there, also lost her life's work.
"I don't know if I'm going to be able to create again," she said.
A total of 150 firefighters worked to extinguish the flames, though no injuries were reported. By 7 a.m., the fire had been put out.
No evacuations were ordered but firefighters managed to protect a nearby retirement home from the flames.
City News Service contributed to this report.