TAIPEI (Taiwan News) — The Taiwan Coast Guard is investigating wreckage that washed ashore on Green Island, off Taiwan’s east coast.

Two pieces of lightweight metal that appear to belong to an aircraft were discovered along the island’s north coast on Saturday afternoon. The first piece, measuring about 200 centimeters in length, was found on the shore near Liumagou, while the second, about 300 centimeters long, was discovered near Chaikou Beach, about two kilometers to the west, per LTN.

The pieces are painted white and have rivet marks characteristic of an aircraft’s wing or fuselage. Marks on the material in some places suggest the craft was damaged in an explosion.

It was speculated that northeast monsoon storms may have dredged up wreckage from the seafloor and brought it ashore. The Coast Guard was dispatched on Sunday to retrieve and inspect the debris, and military analysts will work to identify its origin, per UDN.

Upon preliminary review, personnel from Chihang Air Force Base in Taitung said the debris does not resemble any aircraft operated by the Air Force in the area, per UDN. However, they did not rule out the possibility that the wreckage was part of a foreign aircraft, a rocket or space vehicle, or possibly a large drone.