DHA news agency said initial findings suggested the blast occurred when an overhead crane collapsed into a large industrial furnace used during the liquid steel casting process.
Izmir Mayor Cemil Tugay said rescue teams were "continuing their work to remove the collapsed platform" and that those affected were factory workers.
"Unfortunately, we have received preliminary information indicating a large number of deaths and injuries among people working at the factory. The exact number will become clear once the wreckage has been removed," he said in a post on X shortly before the initial toll was given.