All of the water that's been poured on a stubborn south side warehouse fire has created a new concern: an unplanned collapse.
"There's a big concern of collapse," said Deputy Fire Commissioner John McNicholas. "We know the structure's been compromised from the fire as well as the ice that's sitting on it. There's probably a good coating of six to eight inches on the front. That's pulling on that structure. If I have a shift of any load on the inside, yes, the building could subsequently collapse more."
Despite the danger, the crystalline castle continued to impress passersby and photographers.
"I've never seen anything like that before. It's beautiful but kind of unfortunate," said Susie Moya.
The Chicago Fire Department on Thursday brought out a new piece of equipment -- a deluge unit -- after a "significant rekindle" of the fire that started two days earlier. The vehicle combines up to 10 hose feeds into a couple of powerful blasts.
"These units can shoot large amounts of water, over 4,000 gallons a minute, long distances. We're not putting the firefighters in harm's way," said Fire Commissioner Jose Santiago.
But with temperatures in the low 20s Thursday, all that water continued to freeze, exacerbating the threat of a collapse.
Even while the firefight continued, department officials said their investigation into a cause was already under way.
"We know the general area of where it started. We're very fortunate that we had a battalion chief that was passing by the area who actually saw where it started. So we know where to look for, we're just trying to make it safe so we can get in there and take a look," said Santiago.
The building has already been deemed a total loss and will be demolished. Officials just want it to come down safely and on their own terms.