Ten Turkish seafarers are missing after general cargo ship Tuğberk İmamoğlu collided with chemical tanker Alsu in the Marmara Sea and is believed to have sunk, according to the Istanbul Governor's Office.
The two Turkish-flagged vessels collided at about 03:15 roughly 18 nautical miles, or 35 km, south of Istanbul's Silivri district.
Tuğberk İmamoğlu was sailing from İskenderun to Karadeniz Ereğli, while Alsu was heading from Kocaeli to Aliağa.
A COSPAS-SARSAT EPIRB distress signal from Tuğberk İmamoğlu was received at 03:26. At 03:41, the master of Alsu told vessel traffic services that his ship had collided with an unidentified vessel.
The first maritime rescue unit headed to the casualty site at 04:10. Transport and infrastructure minister Abdulkadir Uraloğlu said Tuğberk İmamoğlu was believed to have gone down in about 11 minutes. All 10 people aboard, including the captains, were Turkish nationals. No crew member had been reached alive at the time of his statement.
Lifesaving equipment from Tuğberk İmamoğlu, including its free-fall lifeboat, was later found floating without any crew aboard. Water depth at the casualty site is about 800 to 900 metres.
The search involved two coast guard helicopters, nine coast guard vessels and three Directorate General of Coastal Safety craft. A UAV, one frigate, two other naval vessels and a fast-attack craft were also assigned to the operation.
Tuğberk İmamoğlu was carrying 4,199 tonnes of rolled steel, with a later official update specifying rolled sheet metal and reinforcing bar. Initial official information put Alsu's cargo at 2,999 tonnes of motor oil, while a subsequent update stated that the tanker was empty. Initial inspections found no visible damage to Alsu.
The Silivri Chief Public Prosecutor's Office opened an investigation and ordered the preservation and collection of voyage, radar, communications and other vessel records.