SAN DIEGO () As illegal land crossings at the southern border have declined, the Trump administration has shifted part of its focus to maritime borders, where the U.S. Coast Guard is facing persistent smuggling activity.

Coast Guard crews operating near San Diego are intercepting smugglers using increasingly organized operations to transport migrants and contraband into the United States by sea, officials said Monday.

Coast Guard personnel employ a three-step approach when confronting suspected smuggling vessels: issuing verbal warnings, firing warning shots and when necessary, using pepper balls and disabling engines.

Chief Peter Nelson, officer in charge for Coast Guard Station San Diego, described escalating confrontations with smugglers.

“The majority of the time, they do comply with what we need them to do,” Nelson told . “But there have been some incidents where they have taken evasive actions with their vessel, where they’ve driven their vessel into the side of our boat. They have thrown objects at us. They’ve thrown tools at us.”

Authorities have intercepted individuals with criminal backgrounds, including at least one known gang member with previous felony drug charges.

To address the persistent maritime smuggling, officials have deployed additional resources, including Coast Guard crews from Hawaii, a helicopter unit from San Francisco and a Navy destroyer.