Firefighters continued to spray water on the remains of the construction site throughout the day and from time to time, smoke and flames could still be seen rising from the charred remains.
The fire is under control, but not necessarily contained. The danger is far from over.
"It's likely to collapse," said Chief Hayes-White. "I'm not a structural engineer, but given the amount of fire damage and water being applied it weakens the structure even further."
The massive fire erupted around 5 p.m. Tuesday. Flames raced through the apartment building, which was under construction, and shot into the air. Over 150 firefighters, half of the firefighters in San Francisco, responded to the blaze.
"I'd say in my career this is the biggest volume of fire that I've ever seen," said SFFD Deputy Chief of Operations Mark Gonzales. "I mean, just the size of it."
Even though investigators have not yet been inside the structure, the fire chief says they're already looking at a possible cause.
"There was some torch work, some welding work being done, and then they got off around 3:30 or 4 p.m.," Chief Hayes-White said. "That's something we're looking at, it's still preliminary."
The chief says there were a few workers still on site when the fire broke out. But it's not clear if they were the ones who'd been welding.
San Francisco Mayor Ed Lee came to see the damage Wednesday morning. He says that as bad as it is, it could have been worse.
"This is part of Mission Bay," Mayor Lee said. "When I was DPW director, we focused on building an infrastructure. Part of that infrastructure was the auxiliary high pressure water system."
The fire chief agrees. The water supply made a big difference. But it was still a hard fought victory over the flames. And a firefighter was hurt in the fight.
"When he was up on the ladder, did sustain some burns to his face," Chief Hayes-White said. "I saw him continuing to battle the fire. Wasn't until later that he indicated he had some minor injuries."
That firefighter and a battalion chief who hurt her ankle during the overnight watch have both been treated and are now back home.
The fire chief says that when they're finished spraying water on the fire, and there's no estimate as to when that will happen, she says that's when structural engineers will come in and talk about dismantling whatever's left of the structure.
The real estate development company BRE Properties was building the complex, called MB360. 172 apartments were under construction at the time of the fire. The units were expected to run about $630,000 each when finished later this year. BRE says it has insurance and believes the losses will be covered.
BRE issued a statement about the fire saying, "Thankfully, the project was safely evacuated and all associates and contractors have been accounted for. We extend our thanks and gratitude to the fire and emergency services personnel for their rapid response."
There was no sprinkler or fire suppression system in the building -- that's something the fire department says they may start requiring in construction projects in the future.
Mission Bay residents begin to return home
The building that burned wasn't scheduled to open until August, so no one was living there, but residents in neighboring building were told to leave. Wednesday evening, some of the evacuation orders had been lifted but other residents were still waiting to hear when they would be able to return home.
One of the tires on Laurel Kilgour's bike melted in the heat from the fire and there are cracks in some of her windows. But she says most of the damage she saw as she returned to her apartment across the street from the fire was in the hallways where fire crews came through.
"It's llike they walked through with pick axes or something," she said.
Firefighters describe battling blaze
Firefighter Stephen Maguire has been on the scene since the flames erupted Tuesday evening and he's not scheduled for a day off until Thursday.
"You're just working on adrenaline and don't even realize how many hours have gone by," he said.
Maguire's ladder truck responded to the first alarm of what would become a fast moving five-alarm inferno.
"I was hoping it wasn't going to be the huge monster it turned out to be," he said. "We were hoping to stop it where it began."
That's what another firefighter on the same rig, Lt. Ramon Serrano, hoped too. He was one of the firefighters up on ladders performing what he calls a "surround and drown" operation. Serrano was eventually was ordered down because of the danger.
"It just got intensely hot and the flames started coming out of all the windows and black smoke started pouring everywhere," Serrano said. "It was enough for me to turn my head down to help my helmet shield me from the heat."
When you look at what the firefighters were up against, it seems a miracle they kept the flames from burning other buildings. Wednesday, the fire chief said the crews did a phenomenal job.
"We don't get these types of fires every day, but we train for this type of conflagration and we were up to the task last night," Hayes-White said.
ABC7 News reporters Katie Marzullo, Cornell Barnard, Matt Keller, Wayne Freedman and Carolyn Tyler contributed to this report.