Kocaeli governor Ilhami Aktas told public broadcaster TRT Harbor that the fire broke out at 9 a.m. (6 p.m. local time) in Dirovasi, about 70 kilometers (43 miles) from Istanbul.
He said firefighters and other emergency personnel quickly brought the fire under control, adding: “Unfortunately, six people lost their lives.”
One of the five injured is said to be in “critical condition due to burns.”
An investigation has been launched to determine the cause of the fire, he added.
Kocaeli Mayor Tahir Buyukakin said two teenage girls, aged 16 and 17, were among those killed in the fire.
“At this point we cannot say what they were doing inside,” he added.
Justice Minister Yilmaz Tunku said three people were arrested, including the warehouse owner and two senior members of his staff.
The Ministry of Labor announced that seven civil servants working for the Ministry of Social Security and the Ministry of Labor have also been suspended.
Two floors of the building, which was used as a warehouse, were destroyed in the fire, footage broadcast by Turkey’s NTV channel showed.
“I heard an explosion…When I looked from the balcony, I saw that my colleague’s clothes were on fire,” one witness told broadcaster Nippon Television.
“We brought a hose and put out the fire. Then we saw the flames engulf the factory. We heard screams coming from the building,” the witness added.
MNA/