South Korea’s unification ministry has urged private groups and individuals not to send leaflets and other items into North Korea, confirming that police are investigating a reported leaflet launch by defectors.

The group of defectors sent 120,000 leaflets and 3,000 USB flash drives over the border by balloon earlier this week, according to private ROK broadcaster Free North Korea Radio. This would make the group the second to publicize leaflet launches in recent years, after Fighters for a Free North Korea.