Venezuela on Thursday authorized two very large crude carriers (VLCC) to set sail for China, according to two sources familiar with the South American country’s oil export operations, which would be only the second and third supertankers to depart the nation since the U.S. seized a ship carrying Venezuelan oil last week.

The U.S. has said it would not allow vessels under sanction to leave Venezuelan waters. The departing tankers, each carrying around 1.9 million barrels of Venezuelan Merey heavy crude, according to internal documents from state company PDVSA, are not on the current U.S. sanctions list.

The ships plan to navigate with their tracking transponders switched off from Venezuela’s main oil port of Jose, one of the sources said. One of them had already sailed away from Jose’s anchorage, where many loaded vessels have been waiting for instructions to depart since the U.S. seized the ship last week, monitoring service TankerTrackers.com said after analyzing Thursday’s satellite images.