Gerretsen told CBC's Ottawa Morning host Robyn Bresnahan that he wondered about the large wooden structure as it was being built.
"I'll be the first to admit — driving by this building, and I did on a daily basis — as I saw the wood structure go up, and having some experience in the construction world outside of my business at City Hall, I thought to myself, 'Well, this is a pretty big structure to be made out of wood entirely.' So I think that the concerns are valid. I think that many members of the community shared that concern."The fire, meanwhile, is still burning at the construction site, Gerretsen said. Because firefighters can't get close enough until the crane is dealt with, they can't douse the remaining flames and hot spots.
Staff with the Office of the Fire Marshal of Ontario, the Kingston fire department and Ontario's Ministry of Labour were planning how to move forward.
Everyone within a two-block radius of the structurally compromised crane were still waiting to return to their homes Wednesday morning.
"There was a point yesterday where we were pretty much certain that the crane was going to fall over," Gerretsen said Wednesday morning. "But we did have engineers on site last night, who are back again this morning, who are determining if it falls, how it's going to fall.
"Being right in the middle of a populated downtown part of the city of Kingston, there are several buildings that ... the crane could actually collapse onto."
Gerretsen stressed that the city has no say over the materials used in the construction of any building.
"That is all entirely regulated by the Ontario Building Code and provincial legislation," he said. "What I can tell you is that a proper building permit was taken out, and that according to the design, it adhered to the building code. ... I am by no means an engineer. Those are the professionals that are going to know more concretely as to what is appropriate and what isn't appropriate."
Gerretsen also said that if the building had been finished, with sprinkler systems and fire-retardant drywall in place, the situation may have been a lot different. He also said it's too early to know what caused the fire.
"It's all speculation at this time, and it's very difficult to comment any further on it or go into any great detail before we know exactly what's going on here," he said.
The fire began at about 2:20 p.m. ET Tuesday at a student housing complex under construction near the 600 block of Princess Street, according to Kingston police Const. Steve Koopman. The building, which was vacant, was engulfed in flames.
The fire also spread to the roof of a Royal Canadian Legion villa.
Power had to be shut off in the area around the fire and residents living within a half-kilometre of the fire were taken to an emergency shelter at the Portsmouth Olympic Harbour at the bottom of Yonge Street.
Any affected residents who had nowhere else to go were put up in hotels by the city, Gerretsen said.
Police said residents have been asked to stay away from the current perimeter of the fire, from Concession Street to the north and west, Albert Street to the east and Dundas Street to the south.
They said they'll be advising residents when they can re-enter the evacuation zone for pets or other items.
The developer of the property, Patry Inc. Developments, issued a statement on Facebook Tuesday thanking "Kingston Fire Rescue, Kingston Police, Kingston EMS, Trenton Search and Rescue, neighbouring fire departments and all other individuals/organizations who assisted today to extinguish the blaze and prevent loss of life.
"For individuals who have signed leases beginning September 2014, Patry Inc. will be in touch in the near future as the situation is assessed, more information becomes available, and all options are considered," the statement said.
Construction at the site was being overseen by Stelmach Property Management.
The military rescue technician who was lowered from a helicopter to save the crane's operator, stranded above the flames, credits daily training for the success of the "extremely unusual rescue."
Sgt. Cory Cisyk, a search and rescue technician for 424 Transport and Rescue Squadron based at 8 Wing Trenton at CFB Trenton, recounted the rescue to CBC's Ian Hanomansing Tuesday night.
Cisyk, originally from Regina, was aboard the CH-146 Griffon rescue helicopter that arrived at the scene above Princess and Victoria streets before 4 p.m. Tuesday to reach the worker, who was trapped high in the air while fire crews worked to put out a blaze below.
Cisyk said that as they were flying to the location, they didn't know what to expect, but the crew had a couple of different plans.
Based on the information they received, they planned a "double-up" rescue in which Cisyk would be lowered from the chopper on a cable and then use a strap or "horse collar" to wrap around the crane operator to pull him up.
Cisyk said that when he first made contact with the crane operator, it was difficult to communicate with him because of the noise from the helicopter.
"I kept asking if he was OK. I kept telling him I was trying to get him out of there."
Cisyk said it took time to get the collar around the man because he was lying down at the end of the crane's boom, but that he got some help from the helicopter flight engineer.
"He could tell I was having a hard time getting the individual to stand up, so he was gently hoisting to aid me."
Once he got the crane operator in the chopper, Cisyk said, he had only a brief conversation with him to find out if he was hurt. The man was taken to hospital with minor injuries.
"For us, this was extremely unusual. But even discussing with the crew afterwards … we really figured that the training we do every day really came into it and played a big factor in ... the way things ran."
The crane operator remained in hospital Wednesday morning.
John Ashie, who was working at his family's car dealership down the street, said the entire episode was like something out of an action film.
"Especially when the helicopter guy was rescuing him from the crane, everyone was like, 'Oh my god! I can't believe this is happening, it's just so surreal,"' said Ashie.
David Elias, a civilian public affairs officer working for the Canadian military, said the crews are normally not involved in urban rescue.
"The number of times we would have hoisted someone off a crane like this, I imagine we could count that on one hand. Normally we are hoisting people off of boats or mountains," said Elias.
"He wasn't just standing on a tower crane. He was standing on a tower crane surrounded by flames."
All construction workers at the site are believed to be accounted for, according to Kingston police.
"We're extremely grateful of the amazing work done by CFB Trenton to rescue that one individual that everybody was worried about," Gerretsen told CBC's Power & Politics host Evan Solomon on Tuesday. "This is a day that the public can be extremely proud of your emergency workers. Right throughout the province, people from neighbouring communities, fire and rescue have been coming into Kingston to assist."