WESTBROOK, Maine (AP) — A swirling disk of ice on a Maine river is drawing onlookers in the heart of winter once again.

The disk has formed in the Presumpscot River in Westbrook. A handful of dog-walkers and onlookers stopped to gaze at the curious ice formation on a chilly Thursday morning around dawn.

The disk drew fans from around the globe when it first appeared in the river in 2019. It also partially formed in 2020.

Ice disks can form because of a current and vortex under ice. The ice sheets spin and form into circles. Officials with Westbrook have cautioned against attempting to go out on the ice disk.