Greek owners feature heavily on a list of tankers detained in Yemen by Houthi militias.
Saudi Arabia has said it fears the vessels will be destroyed as part of the civil war that is tearing the country apart.
A list provided to TradeWinds by the Embassy of Saudi Arabia shows 17 tankers, a gas carrier and a bulker carrying wheat have been held at the port of Hodeidah for more than 26 days in some cases.