Five different vessels ranging from airplanes to helicopters and heavy ice breakers were deployed in Lake Huron to search for the octagonal object, but it was never recovered.
The Coast Guard says it conducted 23 searches in northern Lake Huron covering 4,000 square miles alongside Canadian agencies.
Over the course of the three-day search—Coast Guard vessels spent nearly 60 hours searching for the object.
No autonomous underwater vehicles were deployed during the search—instead the Coast Guard says it relied on subsurface radar scans and ariel photos.
US Northern Command has yet to confirm if the object landed fully formed in the water or was destroyed.
