The assertion, which came during Noem's testimony to the House Homeland Security Committee, provided the Trump administration's most thorough assessment so far of why it took control of the vessel on Wednesday.
Seizures of more tankers could put a stranglehold on Venezuela's economy, which is exceptionally dependent on oil to keep the government running and pay for basic necessities.
The U.S. is preparing to intercept more ships transporting Venezuelan oil following the seizure of a tanker this week, sources familiar with the matter said.
Russian President Vladimir Putin has expressed "solidarity with the Venezuelan people" amid growing tensions between Venezuela's leader, Nicolás Maduro, and the Trump administration.