A major fire has destroyed most of Hastings Pier in East Sussex, a day after redevelopment plans were invited.
Two people have been arrested and detained for questioning.
Firefighters have been at the scene since the early hours attempting to save the historic structure. The fire was brought under control at 0800 BST.
A passing police patrol and local people raised the alarm at 0100 BST after seeing a small fire, but the pier was rapidly engulfed in flames.
Residents reported hearing a series of explosions.
The pier opened in 1872 and was originally 910ft (280m) long. It closed in 2006 because of fears it had become unsafe.
On Monday, the Hastings Pier and White Rock Trust invited architects to submit designs to redevelop the attraction.
Fire service spokesman Simon Rose said 95% of the upper structure had been destroyed.
Mr Rose said: "It's a very historic building and landmark for Hastings."
He said the priority for firefighters had been to preserve as much of the structure as they could "to see if something can be done with it in the future".
A fire crew was on the scene within five minutes of the first emergency call.
It was quickly joined by further crews, two RNLI lifeboats and the Sussex Police helicopter.
Some firefighters were taken to the scene by lifeboat.
Mr Rose said no-one was injured and the cause of the fire was still unknown.
Insp Lee Lyons said officers had come across the fire at the same time that fire crews were receiving the first emergency calls.
He said: "It was very small at that stage, but it took hardly any time to engulf the pier."
He said the entire ballroom had become a burning framework with bits dropping off into the sea.
The owner of a bed and breakfast opposite the pier said he heard a series of blasts as the structure caught fire.
Dale Turner, 55, who owns the Seaspray B&B, said: "This is the sort of thing people were worried about. The pier had been allowed to fall into ruin and now we may never get it back."
Campaigners had been fighting to secure the pier's future.
Earlier this year, Hastings Borough Council agreed to buy the pier with a compulsory purchase order and hand it to the Hastings Pier and White Rock Trust.
The pier was owned by Panamanian-registered company Ravenclaw, which the council said it had been unable to contact.
The decision followed a study which showed the sub-structure could be made safe for £3m.
After the fire, Councillor Jeremy Birch, leader of Hastings Borough Council, said: "We are very disappointed that this fire has taken most of Hastings Pier's upper levels with it.
"Firefighters have worked heroically to try and contain the blaze but unfortunately, because of the wind, the state of the pier and the danger of going on it, the fire really took hold."
He said the local authority would now look at a new structural survey in order to be absolutely clear on the degree of damage to the sub-structure.
Mr Birch said: "Then we can see what the future holds for this iconic building on our seafront."
Felix Robinson, outgoing chairman of the Hasting Pier and White Rock Trust, said it was a sad day for the town.
He said: "I always knew that the pier was at risk of fire, when it was closed and empty. But to actually see it go up in such a massive fire is very sad."
He said many people - some in their dressing gowns - had come out along the seafront and stood watching the blaze.
Shock and disbelief
"There was a sense of sadness," he said. "People were talking about the experiences they'd had in the past - and of course the ballroom at the end, which is completely gutted, was quite important for Hastings in a cultural sense."
The council and the trust vowed not to give up hope that something could be saved and spent the day in a series of meetings with the emergency services.
Mr Robinson said one part of the pier that was still standing was the area where people liked to gather as the sun went down.
"Piers have suffered fires in the past and been restored," he said. "And the reason is the cast iron pillars that go down into the seabed. They tend not to be too much affected by a fire of this nature."
Fire crews began to scale down their operation on Tuesday morning but the pier was still producing a thick plume of smoke.
People were advised to avoid inhaling the smoke unnecessarily by keeping away from the area, and residents should keep their doors and windows closed.
Police have been questioning two teenagers, aged 18 and 19 and both from St Leonards, on suspicion of arson.
Sixty firefighters were at the scene at the height of the incident. Their priority was to preserve as much as the structure, including the main steelwork, as possible.
Long traffic delays were reported around the area after the A259 was closed in both directions. Motorists were advised to make only essential journeys with the road closure due to remain in place for some time.
Campaigners have been writing about their shock and disbelief on the Facebook page, Save Hastings Pier, which has more than 1,600 members.