SEOUL, South Korea (AP) — Six U.S. citizens were taken into custody on Friday in South Korea for attempting to send 1,600 plastic bottles containing rice, small Bibles, $1 bills, and USB drives towards North Korea via the sea, according to police reports.

These individuals were detained on Gwanghwa Island, which is a front-line location, before they could release the bottles into the ocean with the intention of having them drift to North Korean shores with the currents, two officers from Gwanghwa police indicated. The detainees are under investigation for potentially breaching laws concerning safety and disaster management.

The officers, who asked to remain unnamed as they were not authorized to discuss the matter publicly, declined to provide personal information about the Americans, adhering to privacy regulations.

Gwanghwa police said they haven’t found what is on the USB sticks.

The U.S. Embassy in South Korea had no immediate public comment.

For years, activists have sought to float plastic bottles or fly balloons across the border carrying anti-North Korea propaganda leaflets and USB thumb drives carrying South Korean dramas and K-pop songs, a practice that was banned from 2021-2023 over concerns it could inflame tensions with the North.

North Korea has responded to previous balloon campaigns with fiery rhetoric and other shows of anger, and last year the country launched its own balloons across the border, dumping rubbish on various South Korean sites including the presidential compound.

In 2023, South Korea’s Constitutional Court struck down a controversial law that criminalized the sending of leaflets and other items to North Korea, calling it an excessive restriction on free speech.

But since taking office in early June, the new liberal government of President Lee Jae Myung is pushing to crack down on such civilian campaigns with other safety-related laws to avoid a flare-up tensions with North Korea and promote the safety of frontline South Korean residents.

On June 14, police detained an activist for allegedly flying balloons toward North Korea from Gwanghwa Island.

Lee took office with a promise to restart long-dormant talks with North Korea and establish peace on the Korean Peninsula. Lee’s government halted frontline anti-Pyongyang propaganda loudspeaker broadcasts to try to ease military tensions. North Korean broadcasts have not been heard in South Korean front-line towns since then.

But it’s unclear if North Korea will respond to Lee’s conciliatory gesture after vowing last year to sever relations with South Korea and abandon the goal of peaceful Korean reunification. Official talks between the Koreas have been stalled since 2019, when U.S.-led diplomacy on North Korean denuclearization derailed.