A 42-year-old man remains in Whanganui Hospital in a stable condition following the "massive blaze" which engulfed a heritage building in central Whanganui on Saturday night.
The other who was hospitalised, a 46-year old male, has since been discharged.
The cordon which was in place around the building on the corner of Taupo Quay and Victoria Ave was lifted late on Sunday morning.
Whanganui fire chief Gary Ward said the crews "did an amazing job containing a very large fire".
Ward said the roof and internal floors of the building have collapsed.
He said the fire was contained to the one building but others close by may have sustained heat or water damage.
Eleven fire crews from as far away as Palmerston North and New Plymouth rushed to the fire after multiple calls came in from 8.45pm.
Crews took until 12.55am to put the fire out.
Both those caught in the fire had been treated for burns and smoke inhalation and taken to Whanganui Hospital.
Artists from MINZ - made in New Zealand gift shop on the ground floor of the Thain's building don't know when they will be allowed inside to assess the damage.
Bruce Kelly, a member of the MINZ collective said the group was not insured and individual artists will bear the personal risk of losing their stock.
"The main thing is that no one was killed in the fire," he said.
Whanganui Mayor Hamish McDouall said an engineers' inspection of the building will be completed "relatively quickly" so the intersection of Taupo Quay and Victoria Ave can be reopened.
"At the same time we need to ensure that there is no danger to the public as the top two floors have gone."
Whanganui's new LJ Hooker franchise had set up shop on the ground floor of the Thain's Building last month.
"It is such a shame," agent Tim Hocquard said.
"We were just starting to gain momentum but it is not so bad for us. We get a lot of our business online and we should able to find a new shop front premises - but I feel for others who are worse affected."
Hocquard said he felt badly for the injured man in hospital and the owner of the Thai Villa restaurant next door which had to close.
He said the interior renovations in the building were going well and the upper floors had been "beautifully restored".
"I really feel for the owner and the builder because they had put their hearts and souls into it," Hocquard said.
Whanganui artist Bernie Steyn lives in a building diagonally opposite and was evacuated after the fire started.
"I didn't think I was in any danger but my power had gone out," he said.
"I watched the fire crews working and I was really impressed with how well they managed to contain the fire."
Steyn did not know when he would be allowed to return to his home.
"I hope it's soon because I only have the clothes I'm wearing and my phone."
Unable to open his Victoria Ave Jolt Cafe on Sunday morning due to the cordon, owner Mark Dyhrberg parked his truck in nearby Ridgway St and used a generator to power up his coffee machine.
"I didn't want to let my regulars down," he said. "Thankfully there doesn't appear to be any damage to the cafe for which I'm very grateful."
Kelly said he felt for building's owner, Bryce Smith, who had put so much work into restoring the heritage building.
"We were due to close on July 31 so renovations could get underway on the ground floor and now we're closing because of fire."
At the height of the fire more than 100 people gathered outside in shock, with a eye-witnessed describing it as a "massive blaze".
"I was driving home and I just looked up and I could just see huge flames, like crazy big flames, it was pretty scary," witness Maddy Stoneman-Boyle told the Herald.
She said smoke was billowing more than 50 metres above the burning building.
Photos posted on social media showed smoke billowing from a building at the bottom of Victoria Ave, near the river.
A witness told the Herald several nearby restaurants had been evacuated.
Dozens of comments of people in shock were being posted in response to photos of the blaze.
The fire was at heritage Thain's building at 1 Victoria Ave which was sold after an earlier consent to demolish it had been declined.
The Thain's building is a Class B heritage building in the Whanganui District Plan but has no national heritage status.
The three-storey unreinforced masonry building is severely earthquake-prone at 5 per cent of new building standard (NBS) and the ground floor was flooded in the June 2015 floods.