A U.S. military drone strike on a suspected drug-smuggling vessel in the Caribbean Thursday left two to three survivors, according to a U.S. official.

The large vessel was operating in international waters when it was hit, leaving it partially submerged.

Search and rescue efforts were launched, though it remains unclear if any survivors were recovered or the extent of their injuries.

The strike marks the first known incident with survivors since the U.S. began its lethal campaign against drug boats last month, Fox News has reported.

This was the sixth known strike in the escalating operation, part of President Trump’s effort to dismantle transnational cartels by force.