Turkish authorities searched a German-owned ship on Thursday over allegations that it might be carrying Iranian weapons bound for Syria.
The Antigua and Barbuda-flagged Atlantic Cruiser was halted in the Mediterranean last week.
The vessel then changed course and docked at Turkey’s southern port of Iskenderun where the search is being carried out.
Owners Bocksteigel said a group calling itself the Syrian Revolution Naval Forces sent the German shipping firm an email claiming there are arms onboard.
Bocksteigel and the Ukrainian company chartering the ship deny the claims.
The EU and Turkey are enforcing an arms embargo against Syria over its crackdown on a popular uprising against President Bashar Assad’s rule.