Washington — A U.S. Customs and Border Protection (CBP) agent died and several others were “gravely wounded” after exchanging gunfire with a suspected smuggling vessel off the coast of Puerto Rico, U.S. government officials said Thursday.

The gun fight occurred early Thursday morning after three agents from CBP’s Air and Marine Operations branch intercepted the vessel 14 miles off the coast of Cabo Rojo, a community in Puerto Rico’s southwestern corner, CBP said in a statement. The agents, CBP said, “suffered various gunshot injuries” and were airlifted to a trauma hospital near San Juan.

“The event is currently under investigation,” CBP added.

Two CBP officials who requested anonymity to discuss internal notifications told CBS News that one of the agents involved in the incident has died. During a hearing before a Senate committee Thursday, Homeland Security Secretary Alejandro Mayorkas, who oversees CBP agents, acknowledged the agent’s death.

“Ranking Member (Rob) Portman mentioned the tragic loss of one of our front-line personnel. Several others were gravely wounded. I was briefed on the situation very early this morning. These are brave members of our Air and Marine Operations within U.S. Customs and Border Protection,” Mayorkas told the Senate’s Homeland Security and Governmental Affairs committee.

Mayorkas said he was praying for the swift recovery of the wounded agents.

Additional details about the incident on Thursday morning, including who shot the CBP agents, were not immediately available.

CBP’s Air and Marine Operations branch oversees 1,800 federal agents charged with identifying and stopping unauthorized migrants and illicit drugs and goods approaching U.S. borders. The unit has 240 aircraft and 300 vessels at its disposal.