JACKSONVILLE, Fla. -- The State Fire Marshal is investigating the cause of a fire that consumed the rooftop of an apartment complex under construction at St. Johns Town Center on Tuesday.
Hundreds of nearby shoppers watched as the Jacksonville Fire Rescue Department searched for workers who they believed were trapped in the five-story building.
[ST.JOHNS TOWN CENTER FIRE SLIDESHOW]
"All we saw was big black smoke," said Andronicus Jamison. He was one of the first to notice the flames as he walked out of a nearby store.
"It looked like it started in the front but then the back of the building started going up too."
Lynn Goin saw the flames as she drove down JTB, and he immediately called 911.
"They said they were on the way and then I saw a big orange flame shooting straight up out of the middle and then we heard explosions."
[MORE VIDEO OF FIRE]
More than 60 firefighters began battling the fire just before 4 p.m. and Action News was told it was under control within 15 minutes.
JFRD spokesman Tom Francis says the early investigation leads to propane tanks as the cause of those blasts. The tanks are part of construction equipment used to heat foam to build a rooftop deck. That equipment was likely used earlier in the day.
Although the timeline still not clear to investigators, they tell Action News that work on the roof wrapped at 3:30, so workers were already on their way home and no injuries were reported.
The State Fire Marshall is now conducting its own investigation.
Construction began early in 2012, and 130-unit condo for rent community was set to open in June.