SEASIDE, Ore. (AP) β€” Scores of live sand dollars began washing ashore on the Oregon coast Sunday, mystifying locals.

The Seaside Aquarium posted photos of the sand dollars to Facebook on Sunday, reporting that thousands washed up with the afternoon high tides on the south end of Seaside Beach, The Oregonian/OregonLive reported.

β€œAt this time, we do not know what has caused this, and these types of incidents usually have several contributing factors,” the aquarium wrote on Facebook.

Their post received hundreds of comments, many from concerned people who urged locals to rush out and throw the creatures back into the water. However, sand dollars can only live a few minutes out of the ocean, the aquarium said.

Sand dollars are a species of sea urchin covered in tube feet and spines that they use to move and eat. In rough waters they lie flat partially buried in the sand, but in calmer waters they stand upright like wheels. The creatures feed on algae and other small bits of organic material.