The amount of manmade debris, while large, was less than 2 percent the contents of the stomach, The Tacoma News-Tribune reported. Researchers said they do not believe ingesting the items caused the 37-foot whale's death.
John Calambokidis of Cascadia Research Center in Olympia said the debris does suggest there is a problem in Puget Sound. He said the whale had clearly been eating in parts of the sound with large quantities of floating garbage.
"It's not a very good testament to our stewardship of the marine environment," Calambokidis said.
Gray whales consume small marine plants and animals by straining sand through their mouths. They migrate through Puget Sound twice a year as they travel between Baja California and Alaska.
The whale was the fourth to die in the Puget Sound area in two weeks and the fifth so far in the spring migration.
Notable deaths of 2014 [PHOTOS]
Syrian Al Qaida group executes Lebanese soldier