Agents with U.S. Customs and Border Protection exchanged gunfire with suspected smugglers on Thursday. At least one agent was killed and two others were seriously wounded.

The incident happened about 14 miles off the coast of Cabo Rojo, Puerto Rico. A unit from CBP’s Air and Marine Operations was on a routine patrol in a known drug smuggling corridor called the Mona Passage, between Puerto Rico and the Dominican Republic.

A CBP spokesman said one of the two suspected smugglers was also killed during the gunfight. The FBI will lead the investigation into the shooting. CBP said it’s too early to know where the vessel came from, where it was going and what the boat might have been carrying.

The two surviving agents were taken to the Puerto Rico Trauma Center.

CBP’s Air and Marine Operations use aircraft and sea assets to stop the illegal movement of people, drugs and weapons. In fiscal year 2021, the unit seized over a million pounds of narcotics, $73 million in illicit funds, rescued more than 500 people and arrested more than 120,000.

The Associated Press contributed to this report.