The blast occurred around midday (0900 GMT) at the HABAS steel factory about 60 kilometres (37 miles) north of the port city of Izmir, officials said.
An explosion ripped through a steel plant in western Turkey on Monday, killing 17 people, with President Recep Tayyip Erdogan vowing to find out who was responsible.
The blast occurred around midday (0900 GMT) at the HABAS steel factory about 60 kilometres (37 miles) north of the port city of Izmir, officials said.
"Sixteen people lost their lives in the explosion, while 13 others are receiving medical treatment, two of whom are in critical condition," Erdogan said.
"The circumstances surrounding this tragic incident ... how and why it happened, whether there was any negligence and who bears responsibility, will be established."
Health Minister Kemal Memisoglu later updated the figure to 17 after one of those in critical condition succumbed to his injuries.
Footage from the site showed a huge cloud of thick smoke pouring into the sky as flames appeared to engulf a tall structure within the HABAS Demir Celik plant in Aliaga.
Izmir governor Suleyman Elban said the explosion occurred during "a boiler replacement operation" when an overhead crane collapsed into a large industrial furnace used during the liquid steel casting process.
Eyewitness Deniz Ulker told AFP it felt like an "earthquake".