President Donald Trump defended a second U.S. military strike on a boat allegedly carrying drugs from Venezuela, killing three aboard the vessel.

Speaking to reporters in the Oval Office Monday evening, Trump said he had been shown footage of the latest strike by Gen. Dan Caine, chairman of the Joint Chiefs of Staff.

Asked what proof the U.S. has that the vessel was carrying drugs, Trump replied, “We have proof. All you have to do is look at the cargo that was spattered all over the ocean — big bags of cocaine and and fentanyl all over the place.”

The Trump administration has justified the first strike as a necessary escalation to stem the flow of drugs into the United States.

Several senators, Democrats and some Republicans, have indicated their dissatisfaction with the administration’s rationale and questioned the legality of the action. They view it as a potential overreach of executive authority in part because the military was used for law enforcement purposes.

The Trump administration has claimed self-defense as a legal justification for the first strike, with Secretary of State Marco Rubio arguing the drug cartels “pose an immediate threat” to the nation.

U.S. officials said the strike early this month targeted Tren de Aragua, a Venezuelan gang designated by the U.S. as a terrorist organization. And they indicated more military strikes on drug targets would be coming as the U.S. looks to “wage war” on cartels.