CHICAGO (CBS) — One of the three people injured when a wooden water tank fell nine stories on Wednesday has been released from the hospital.

Two other victims remained hospitalized Thursday morning, after they were injured when the tank fell into the parking lot of the 120-year-old Brewster Building, a 9-story apartment building in the 2800 block of North Pine Grove Avenue in the Lakeview neighborhood.

WBBM Newsradio’s Steve Miller reports the building’s owners have hired an engineering firm to find out what went wrong when the water tank fell from the roof.

The Chicago Buildings Department inspected the Brewster’s water tank three and a half years ago. Spokesman Bill McCaffrey said building inspectors found some problems.

“In order to come into compliance with the building code, the owners submitted a report from a licensed structural engineer that deemed that the water tank and its support structure were in safe condition,” McCaffrey said.

Records show the building owner was ordered to relocate the steel bands on the water tank to their original position, and hire a licensed architect or structural engineer to check it out, and submit a report to the city about the water tank.

It was unclear if the problems from 2010 were linked to the water tank collapse.

“It is entirely possible that something else caused this to fail that wasn’t identified in 2010,” McCaffrey said. “It’s difficult to speculate on the cause of the structural failure.”

CBS 2 investigative reporter Pam Zekman reports that building has had a number of problems with city building code violations, including a failed annual inspection in May for elevator problems.

The city has 153 rooftop water tanks, mostly used to control water pressure in the buildings where they are located, according to McCaffrey.

The tank fell into the parking lot behind the building on Wednesday. A man who was getting into a car was swept away by a wave of water when the tank hit the ground, and a woman who was with him was injured by falling debris.

Another woman, who was leaving a building across the alley, also was hurt by falling debris.

At least three moving trucks and several cars were in the alley where the tank fell.

Kathleen Mullins was helping her sister move out of the building at the time.

“I just saw a lot of debris that was on the ground, I saw a lot of water, I saw people crying,” she said. “If you looked down the alley, you just saw people freaking out, running around, trying to get moving trucks out of the way, and then you saw the ambulances coming in.”

A fire department official said others have fallen like the one today, but very rarely.