Brighton council said that there was no way of knowing whether the fire would help or hinder the redevelopment of the pier, much of which will have to be pulled down before reconstruction can begin.
A spokesperson said that nobody would know whether the fire would affect the redevelopment until a structural report was carried out.
The spokesperson said: "The suspicion is that it was arson. Nobody can see how the pier could have spontaneously combusted."
The Brighton West Pier Trust and developer St Modwen remain confident that restoration works will go ahead as planned.
The chief executive of the West Pier Trust, Geoff Lockwood, said: "Despite this latest setback, we remain totally committed to the authentic restoration of the West Pier."