Michio Kanda was trying to fly from Japan to Oregon.
An airplane searching Thursday about 400 miles south of Umnak Island in the Aleutians was unable to find the 58-year-old balloonist or debris.
Air searchers Monday marked the location of partially submerged white and blue cylinder-shaped objects and a tan object. The debris was not positively identified as Kanda's wreckage.
Kanda reportedly carried a survival pod, cold-weather survival gear and food and water.
The Coast Guard says a manually activated emergency locator beacon was never detected.