Park officials are investigating after a shoe was seen floating in a Yellowstone hot spring—with part of a foot still inside. An employee spotted the shoe Tuesday afloat in the Abyss Pool in the southern part of the park, 30 minutes from Old Faithful. Park officials had no updates on the mysteriously detached body part as of Thursday, according to the Associated Press. The pool is one of the deepest at Yellowstone, according to the Park Service’s website, measuring 53-feet deep, and can reach temperatures up to 140 degrees Fahrenheit. The park temporarily closed the West Thumb Geyser Basin, where the pool is located, upon the discovery of the foot. However, that area has since been reopened, according to a statement by park spokeswoman Morgan Warthin.