The explosion occurred in the mid-afternoon of August 7 - Derince Mayor Zeki Aygün told local media.
The blast originated from a government-owned grain warehouse and felt like a powerful earthquake - Aygün and witnesses said.
Kocaeli Provincial Governor Seddar Yavuz said 10 people were injured, two of whom were in critical condition at a nearby hospital.
Security camera footage recorded the moment of the explosion, showing debris spreading across a nearby cargo yard. A video footage from a distance shows a cloud of smoke and dust rising over the port after the blast.
Derince in Kocaeli province, about 90 km east of Istanbul, is one of the few seaports in Turkey that are fully owned by the government.
Derince is a grain transit hub and regularly receives shipments of grain from Ukraine until the Black Sea grain deal expires last month.
Mr. Yavuz said that the explosion occurred while grains were being transported from ships to warehouses and could have been caused by "growth dust compression".
According to live data from MarineTraffic.com, a shuttle ship flying the Marshall Islands is anchored next to the silos.
The provincial government said 13 of the 16 silos at the port were damaged in the blast. Emergency services are still working at the scene and the police have opened an investigation into the incident.
