Sussex Police say two arson attacks on Brighton's historic West Pier are not being linked.
Detectives investigating a second fire to have been deliberately started on the Victorian landmark say there is no evidence to suggest it is linked to a blaze at the end of March.
The attacks reduced the historic pier to a smouldering shell and the lack of progress in catching those responsible led to Hove MP Ivor Caplin urging officers to pull out all the stops.
His plea came after he heard that the cause of the blazes may never be discovered because the structure was so badly damaged it was too dangerous to inspect.
Mr Caplin said: "Arson on this scale is always a very serious matter. Those responsible for the damage to the pier are criminals and must not be allowed to get away with it.
"I call on Sussex Police to make all the efforts they can to bring the people involved to justice."
Brighton and Hove CID say they are still looking for new leads.
Detectives believe there may be people who were walking or driving along the seafront near the pier at the time who saw something or someone acting suspiciously.
Detective Constable Duncan Chalmers, of Brighton and Hove CID, said: "I'm asking people to cast their minds back and think of anything they noticed, however insignificant they thought it was at the time.
"It could provide the lead we need to solve this arson."
Anyone with information can call Mr Chalmers at Brighton police station on 0845 6070999 or Crimestoppers in confidence on 0800 555111. The reference number is 170:10:05:2003.
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