A strike Thursday brought the death toll from the Trump administration’s military action against vessels in the region to at least 28.

It is believed to be at least the sixth strike in the waters off Venezuela since early September, and the first to result in survivors who were picked up by the U.S. military. It was not immediately clear what would be done with the survivors, who the people said were being held on a U.S. Navy vessel.

They confirmed the strike and the seizing of survivors on the condition of anonymity because the attack had not yet been publicly acknowledged by Trump’s administration.

Trump has justified the strikes by asserting that the United States is engaged in an “armed conflict” with drug cartels, relying on the same legal authority used by the Bush administration when it declared a war on terror after the Sept. 11 attacks. That includes the ability to capture and detain combatants and to use lethal force to take out their leadership.

Some legal experts have questioned the legality of the approach. The president's use of overwhelming military force to combat the cartels, along with his authorization of covert action inside Venezuela, possibly to oust President Nicolás Maduro, stretches the bounds of international law, legal scholars said this week.