Two ships owned by an Iranian company that the United States has accused of supplying material to Tehran’s ballistic missile program departed a Chinese chemical-storage port this week laden with cargo and headed for Iran, according to a Washington Post analysis of ship-tracking data, satellite imagery and Treasury Department records.

The vessels are part of the Islamic Republic of Iran Shipping Lines (IRISL), a state-owned company under U.S., British and European Union sanctions that has been described by the U.S. State Department as the “preferred shipping line for Iranian proliferators and procurement agents.”