Police have dismissed reports that flares were fired into the pier
Police have said they still have no evidence to prove that a fire which swept through Brighton's West Pier was arson.
The fire destroyed part of the Victorian pier six weeks ago, leaving just a metal skeleton at the pavilion end.
Police said on Tuesday they had now interviewed witnesses, but still had no firm evidence to show the fire had been started deliberately.
Detective Chief Inspector Steve Fowler, of Brighton and Hove CID, said without new facts it would be difficult ever to say how the fire started.
"I think that's probably going to be the case unless somebody can come forward and help us substantially," he said.
"I think we will be in the position where we won't know if it's been started deliberately or otherwise."
Owners West Pier Trust believe the fire on 28 March was started deliberately by someone who did not want to see millions spent restoring the structure.
But police have dismissed reports that someone was seen firing flares into the structure from a dinghy.
Rumours that a speedboat spotted near the pier was involved also proved groundless.
An officer from East Sussex Fire Brigade said the fire had made the 137-year-old pier so unsafe it was too risky to send fire investigation officers on to it, so the cause might never be known.
A £30m scheme to restore the pier, which has been closed to the public since 1975, is still going ahead after it was agreed by Brighton and Hove City Council.