Fire has destroyed an historic building which was undergoing a £4m restoration to become an arts centre.
Flames ripped through the 120-year-old Gwyn Hall in Neath, engulfing the four-storey Victorian theatre.
Police say they are "keeping an open mind" about the cause of the blaze, which destroyed the hall within hours of starting at 2100 BST on Thursday.
Council leaders are "devastated" and said it was a "bitter blow" with the refurbishment close to completion.
Politicians joined local people in voicing dismay at the destruction of the town centre building.
Fire chiefs met scenes of crime officers to investigate the cause.
People were evacuated from surrounding properties and a safety cordon was set up between Orchard Street and London Road.
The roads remained closed on Friday, causing disruption for town centre shops and businesses.
People arriving for work and children being taken to school on Friday morning stopped to watch firefighters on long ladders damping down the fire.
Local councillor David Thomas said: "I'm so sad and upset about the loss of this building.
"It was used by the town for so much - everything revolved around the building. I have seen it this morning and it's a shell.
"It's absolutely destroyed."
Eyewitness Stephen Roberts, 26, who lives nearby, said: "There were flames everywhere and firefighters everywhere trying to get control of the fire.
"I looked out of my window and saw loads of smoke. The building's destroyed - it's sad because it was a really nice place."
Alan Roberts, 61, said he could see the flames a mile-and-a-half away at his home in Cadoxton, Neath.
"It was massive, the flames were lighting up the sky," he said.
"We drove through the town this morning and it's very smoky. It's very sad. We used to go there regularly."
His grandchildren used the hall for school concerts.
"We were only admiring the hall the other day, looking at the new windows they had put in as part of the restoration. It's a big loss for the town."
Welsh Secretary Peter Hain, the town's MP, spoke of his shock and sadness following the blaze.
The night sky is lit by the fire at the Gwyn Hall in the centre of Neath
"The Gwyn Hall was a fine Victorian building that served the people of Neath for generations, hosting many, many tremendous events and concerts," said the MP.
"Its loss will leave a gaping hole in the heart of Neath. The fact that the hall was about to undergo a major refurbishment makes this fire doubly shocking and sad."
Local AM Gwenda Thomas praised the 70 fire-fighters involved in preventing the blaze from spreading.
She said: "I'm shocked and saddened that such an iconic and much loved building by everyone in Neath has suffered such severe damage."
Built in 1887, the Gwyn Hall Theatre was a local landmark and had served as a music hall, for council work and latterly as a music venue.
It was due to reopen as a modern arts centre next spring.
It was set to include cinema facilities, an interactive cafe bar, and state-of-the-art stage and would have provided facilities for concert and weddings.
Before the fire, the council had spoken of how the building would be "returned to its former glory and is once again set to be the hub of cultural activities in Neath."
Derek Vaughan, the leader of Neath Port Talbot Council, said: "We are absolutely devastated by what has happened to the Gwyn Hall. It is a very sad day for Neath.
"The Gwyn Hall is an iconic building that was very close to being completely refurbished as part of a £4m regeneration project."
He praised the work of the fire service and was grateful there were no injuries.
"At this time we do not know what caused the fire," said Mr Vaughan.
"The interior of the building is completely gutted and the roof has collapsed.
"The fire is a bitter blow for the regeneration of the Gwyn Hall. We as a council now have to rise to the challenge that faces us."
Det Inspr David Rees, of Neath Port Talbot CID, said: "We are keeping an open mind at this stage as it is far too early to speculate over any potential causes.
"I would appeal to anyone who may have seen any activity at the site of the Gwyn Hall prior to the fire to come forward with information."
Anyone with information can contact Neath CID on 01792 456999 or Crimestoppers anonymously on 0800 555 111.