The 911 call came at 1:09 a.m. from a passerby: A downtown building was on fire.
Firefighters at Station No. 3 quickly realized they weren't far from the scene, an apartment complex under construction near the intersection of the 101 and 110 freeways. In fact, the blaze was less than 200 yards away.
But by the time the station's doors opened and firefighters rushed out, the building was already two-thirds engulfed in flames.
Los Angeles Fire Chief Ralph Terrazas said at a news conference Wednesday that the sheer "amount of fire" that consumed the seven-story structure made it suspicious.
"Upon leaving their quarters, which is literally across the street, this structure was heavily involved in fire. That's unusual, to have that much fire all at the same time," he said. "That is probably a significant factor we'll have to look at."
The investigation into the cause of the massive blaze that sent one of the Da Vinci Apartments' two buildings up in towering flames earlier this week began in earnest Wednesday, with the arrival of a specialized federal arson investigation team to canvass the 180,000-square-foot site.
Officials cautioned that because of the enormous size of the burn site, it may be weeks or months before they are able to reach a conclusion about how the fire started or whether it was deliberately set.
"The evidence inside that building is going to dictate how long this is going to go," said Carlos A. Canino, who heads the Los Angeles field office of the Bureau of Alcohol, Tobacco, Firearms and Explosives, the federal agency with jurisdiction over arson.
An ATF national response team consisting of more than 20 fire investigators and other specialists was expected to dig through the fire debris, interview witnesses and look through any video footage of the fire.