WASHINGTON (AP) — The U.S. has seized survivors after a military strike Thursday on a suspected drug-carrying vessel in the Caribbean, the first since President Donald Trump began launching deadly attacks in the region last month, a defense official and another person familiar with the matter said Friday.

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 on the condition of anonymity because it has not yet been publicly acknowledged by Trump’s administration.

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

Trump 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.

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 say.

The survivors of this strike now face an unclear future and legal landscape, including questions about whether they are now considered to be prisoners of war or defendants in a criminal case. The White House did not comment on the strike.

Reuters was first to report news of the strike late Thursday.

The strikes in the Caribbean have caused unease among both Democrats and Republicans on Capitol Hill, with some Republicans saying they have not received sufficient information on how the strikes are being conducted. A classified briefing for senators on the Senate Armed Services Committee earlier this month did not include representatives from intelligence agencies or the military command structure for South and Central America.

However, most Senate Republicans stood behind the administration last week when a vote on a War Powers Resolution was brought up, which would have required the administration to gain approval from Congress before conducting more strikes.

Their willingness to back the administration will be tested again.

Democratic Sen. Tim Kaine of Virginia, along with Sens. Adam Schiff, a California Democrat, and Rand Paul, a Kentucky Republican, are bringing another resolution that would prevent Trump from outright attacking Venezuela without congressional authorization.