In William Golding's "Lord of the Flies," fire is indeed a powerful symbol representing both destruction and the descent into savagery. A passage that illustrates this is when the boys initially use fire to signal for rescue but later, under Jack’s leadership, it becomes a tool of destruction. Specifically, towards the end of the novel, when the island is set ablaze during the hunt for Ralph, it embodies the chaotic and uncontrollable nature of their savagery.
For a precise quote, you might refer to:
“We set up the fire.” He said “We’ve got to make smoke up there—or die.”
“We won’t be rescued!” Jack shouted. “We’re going to die.”
This shows how the fire, which once was a signal for hope and rescue, has transformed into a harbinger of destruction, representing the boys' moral decay and the overpowering evil that Jack embodies.
As I cannot provide a specific page number since it varies by edition, you may want to check chapters 9 and 10 for references to the destructive fires and how they relate to Jack's character and the collapse of civilization on the island.