Fire experts suspect an arsonist started a seafront Regency terrace blaze which put scores of people's lives at risk.
No one was hurt in the fire which quickly spread through the four-storey property in Brunswick Terrace, near the Brighton and Hove boundary, at 10pm on Friday.
Witnesses described bright red flames shooting out of the window of the third-floor flat where the fire began.
The inferno, which caused severe heat, smoke and water damage to the building, evoked haunting memories of the 1992 Palmeira Avenue blaze in Hove which left five partygoers dead after a fire was started deliberately.
Following the tragedy, which also involved a Regency terrace, an inquest heard another partygoer, Trevor Carrington, started the fire as a prank.
He was later run down and killed by a truck in what was said to be suicide.
More than 100 people watched as dozens of fire-fighters tackled Friday's blaze, which threatened to spread along the terrace to neighbouring flats.
Fire investigation officers and Sussex Police spent the weekend trying to determine the cause of the fire, which was being treated as suspicious because it spread so rapidly.
About six people were thought to be inside the building when it broke out but escaped without injury after being alerted by fire alarms.
A couple who lived in the building arrived home to find their home ablaze.
They sat outside distraught as firefighters from Roedean, Hove, Brighton, Shoreham and Newhaven tried to bring the flames under control.
The woman, who declined to be named, said: "I don't know what to say. Our whole lives are in there."
Another couple with a young baby were in the flat next door to the blaze when it started.
The mother said: "We didn't hear any alarms.
"We were alerted because someone was beeping their horn outside.
"We smelled smoke, then we looked out of our window and saw flames shooting out and licking the building."
Another resident said: "I was just about to get in the bath when people from the next door flat knocked on the door to tell me to get out.
"There was a danger the fire could have spread. The flames were coming out bright red."
Neighbour Carl Clifton, 40, was having a dinner party with friends when someone in the street buzzed the intercom and told them to get out.
Mr Clifton said: "He told me the building was on fire. You think someone is exaggerating but when we ran out the flames were huge."
Dave Reeding, 47, was woken by shouts. He said: "The flames were just bellowing out.
"I was really worried about it spreading."
Andy Gausden, the fire officer in charge of the case, said: "Smoke alarms were activated.
"Residents tried to reset the panel but when they couldn't realised there was a real fire and we got an early call. The fire developed very quickly which is why it is under investigation.
"Usually with a fire detection system such as this one in place we are able to contain the fire to one room."
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