ISTANBUL — Turkey launched a search operation Wednesday off the coast of Istanbul after two ships collided and contact was lost with one vessel and its crew of 10, officials said.

The collision took place at 3 a.m. in the Marmara Sea a little more than 20 miles (32 kilometers) south of Silivri, a western suburb of Turkey’s largest city, the Istanbul governor’s office said in a statement.

Contact was lost with the crew of the Tugberk Imamoglu, flagged to Turkey, after the collision with the Turkish-flagged Alsu, which appeared undamaged, the governor’s office said.

“Numerous naval units from the coast guard’s Marmara and Bosphorus Command and a coast guard helicopter were dispatched to the scene,” the office added.

The Tugberk Imamoglu, a 90-meter (295-foot) cargo ship, was traveling from Turkey’s Mediterranean post of Iskenderun to Eregli in the Black Sea. The 91-meter (298-foot) Alsu is an oil or chemical tanker sailing from Kocaeli, east of Istanbul, to Aliaga on the Aegean coast, according to the Marine Traffic website.

The Turkish Straits, comprised of the Bosphorus Strait and Dardanelles Strait at either end of the Marmara Sea, are among the busiest shipping lanes in the world, with hundreds of thousands of vessels transiting between the Mediterranean and Black Seas yearly.