Washington — The White House on Monday said a U.S. attack on an alleged drug boat in September included more than one strike on the vessel, seemingly confirming a Washington Post report that the U.S. targeted the boat for a second time to take out survivors of the initial attack.

The Post reported on Friday that Defense Secretary Pete Hegseth gave a verbal order to leave no survivors before the U.S. attack on a suspected drug-smuggling boat in the Caribbean on Sept. 2. The Post reported that the first strike left two men alive in the water. The paper said the commander of the operation, Adm. Frank Bradley, ordered a second strike to comply with Hegseth's directive, killing the two. CBS News has not independently confirmed the Washington Post's reporting. 

The report sparked calls for an investigation by lawmakers of both parties in Congress, some of whom raised the prospect that targeting the survivors could constitute a war crime. Hegseth has called the reporting "fabricated, inflammatory and derogatory," claiming the operations in the Caribbean are "lawful under both U.S. and international law."

White House press secretary Karoline Leavitt was asked about the Post's report during the White House briefing on Monday. "Does the administration deny that that second strike happened, or did it happen and the administration denies that Secretary Hegseth gave the order?" a reporter asked.

"The latter is true," Leavitt replied, before reading out a written statement: "President Trump and Secretary Hegseth have made it clear that presidentially designated narcoterrorist groups are subject to lethal targeting in accordance with the laws of war. With respect to the strikes in question on Sept. 2, Secretary Hegseth authorized Admiral Bradley to conduct these kinetic strikes. Admiral Bradley worked well within his authority and the law, directing the engagement to ensure the boat was destroyed and the threat to the United States of America was eliminated."

At another point, CBS News senior White House correspondent Weijia Jiang asked Leavitt: "So was the initial order from Secretary Hegseth, 'everyone be killed,' and did that come from President Trump?"

"I saw that quoted in a Washington Post story. I would reject that the secretary of war ever said that," Leavitt said. "However, the president has made it quite clear that if narcoterrorists, again, are trafficking illegal drugs towards the United States, he has the authority to kill them. And that's what this administration is doing."

Later on Monday, Hegseth wrote on social media that Bradley is "an American hero, a true professional, and has my 100% support."

"I stand by him and the combat decisions he has made — on the September 2 mission and all others since," Hegseth said.

President Trump said Sunday that he "wouldn't have wanted" the second strike but defended Hegseth's handling of the incident, saying the secretary told him he did not order the subsequent attack.

"The first strike was very lethal, it was fine," the president told reporters on Air Force One, saying he has "great confidence" in Hegseth.

He added: "I'm going to find out about it, but Pete said he did not order the death of those two men."

A group of former military lawyers argued in an assessment on Saturday that the reported second strike would be a violation of international or domestic law. In Congress, the leaders of the House and Senate Armed Services Committees pledged to investigate the matter. And Democratic Sen. Tim Kaine of Virginia said on "Face the Nation with Margaret Brennan" Sunday that the strike "rises to the level of a war crime if it's true," while GOP Rep. Mike Turner of Ohio agreed that it "would be an illegal act" if true.

Former Defense Secretary Leon Panetta, who served in the role from 2011-2013 under former President Barack Obama, said on "CBS Evening News" Monday that the reported second strike constitutes a war crime "because these individuals were injured. They were in the water."

"The basic rules of war that are involved here make very clear that you do not strike wounded people in the water in order to kill them," Panetta said. "You basically then are responsible to try to make sure you do everything to try protect their lives at that point. And that the concern right now whether or not this really violated the rules of war and constituted a criminal act."

On Monday, GOP Sen. Roger Wicker of Mississippi, the chairman of the Senate Armed Services Committee, told reporters that he has spoken with Hegseth and Gen. Dan Caine, the chairman of the Joint Chiefs of Staff, and he plans to talk with the admiral who led the operation. He said Hegseth "did indicate" that "there was a second attack." But Wicker told reporters he did not have information on survivors who may have been killed, adding that he expects to receive that information because "we're going to have all of the audio and all of the video."

The developments come as the U.S. has carried out close to two dozen boat strikes in the Caribbean and eastern Pacific Ocean since the first attack on Sept. 2. 

Asked by CBS News if he has concerns about the boat strikes more broadly, Mr. Trump said Sunday: "Very little, because you can see the boats, you can see the drugs in the boats and each boat is responsible for killing 25,000 Americans."

"The amount of drugs coming into our country by sea is infinitesimal compared to what it was just a few months ago," the president said.