Two vessels linked to subsidiaries of state-owned shipping conglomerate China Cosco Shipping are suspected of having carried Iranian energy cargoes after Washington’s sanctions waiver for China expired on 2 May, according to analytics firm Windward.

The companies, namely Cosco Shipping Tanker (Dalian) Co and Cosco Shipping Tanker (Dalian) Seaman & Ship Management, were put on Washington’s sanctions list on 25 September along with Kunlun Shipping and three other Chinese firms.