Artillery shells found off the coast in Sile, Istanbul Province, date back to World War II, the Turkish Defense Ministry reported.
According to the ministry, it was extremely difficult to determine their origin.
The day before, Turkish navy sappers have completed the inspection of the beach zone, near where about 30 artillery shells were discovered last week, and detonated all the ammunition.
Since Monday, the beaches of Sile were closed. Sappers inspected the beach zones and the area where the shells were discovered. Residents of nearby houses were evacuated for safety reasons.
The Istanbul provincial administration said on July 30 that the Turkish navy had discovered 28 shells on the seabed of the Black Sea while diving in the Sofular area. Eight shells were delivered to the local military base for detonation on the instructions of the Sile prosecutor, while the others were detonated yesterday by sappers.
According to the gendarmerie, no one was injured in the explosions. Residents have been allowed to return to their homes, and the beaches are open except for the one where the explosions took place. It is expected to reopen in the afternoon.
