SEOUL, South Korea (AP) — South Korean officials said Wednesday they suspect that two unmanned drones that crashed recently near the border with rival North Korea were flown by the North on possible surveillance missions.

A drone crashed on frontline Baengnyeong island Monday when the two Koreas fired hundreds of artillery shells into each other’s waters in a flare-up of animosity over a long-disputed sea boundary between the countries. On March 24, another drone crashed in Paju, a South Korean city near the land border with the North.