"It felt like the ground was shifting beneath us, I thought it was an earthquake. When I looked at the factory across the street, thick black smoke was coming out. A fire broke out where the chimney was," Ülker told Anadolu.
"It was like a bomb going off," said Turan Ilbay, who works as a truck driver at the factory and also spoke to Anadolu.
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.