As many as six American citizens were detained by South Korean authorities after allegedly attempting to send plastic bottles filled with rice, US dollars, and Bibles towards North Korea via the sea, police said on Friday, reported AP.

A South Korean police officer, speaking on condition of anonymity, said the group tried to release around 1,600 plastic bottles into the water from Gwanghwa Island, a frontline area near the North Korean border. The aim was for the bottles to drift to North Korea with the sea currents, according to an AP report.

The US citizens are under investigation for suspected violations of South Korea’s laws governing safety and disaster management.