A cargo vessel sank in the Marmara Sea near Istanbul on Thursday, officials said, adding that a search was underway to find the six missing crew.

The Batuhan A, which was bringing dry cargo from Balikesir's Marmara Island to northwest Bursa, took on water and sank off Imrali island, south of Istanbul.

Bursa Governor Mahmut Demirtas said authorities received an "emergency" signal from the vessel but then lost contact.

Demirtas said two coastal safety teams, along with a third group from the Bandirma district of Balikesir province had been dispatched to join the rescue operation of Imrali island.

Rescue speedboats were also urgently sent to the scene, according to a statement by the country's General Directorate of Coastal Safety.

Demirtas added that waves in the area where the ship sank approached heights of 3 meters (11.8 feet), adding that the rescue efforts were being coordinated at the Coast Guard Command of Bursa's Mudanya district.

"The rescue operation continues to find six crew members who are believed to be Turkish citizens," local news channel reported.

Helicopters in the region could not take off because of bad weather.