Traffic in the Bosphorus Strait, an important international shipping lane for oil and grain, was suspended on Thursday morning, data from Turkey's coastal safety agency showed.
The suspension started at 8:45 a.m. (0545 GMT), the agency said, without giving a reason. It was due to end at 6:00 p.m. (1500 GMT).
Turkey's Hurriyet newspaper reported the suspension was part of a search for a 17-year-old boy who had been swept away by the current after entering the Bosphorus on the European side nearly a month ago.
The Bosphorus is one of world's most important choke points for the maritime transit of oil, with over 3 percent of global supply - mainly from Russia and the Caspian Sea - passing through the 17-mile waterway connecting the Black Sea to the Mediterranean.
It also carries large amounts of grains from Russia and Kazakhstan to world markets.
Reporting by Tuvan Gumrukcu