South Korean police have referred six American citizens to prosecutors after they tried to float more than 1,300 plastic bottles filled with rice, one-dollar bills, and Bibles toward North Korea from Ganghwa Island in June.

Authorities said the group, aged between their 20s and 50s, was booked without detention for violating the Disaster and Safety Management Act.

Ganghwa County has been a restricted zone since last year, banning cross-border leaflet and bottle campaigns, with violations punishable by up to one year in prison or fines of up to 10 million won, or about 71-hundred U.S. dollars.

The group claimed the attempt was for missionary purposes, though police found no evidence of backing from religious organizations.

Police said they also handed over the seized bottles as evidence to prosecutors.

Such bottle and leaflet campaigns have often been regarded as sensitive, given the potential for sharp reactions from the North, and the current administration has sought to curb them citing the need to protect border communities and promote inter-Korean reconciliation.