The 20-year-old man, whom authorities wouldn't identify, was dressed in civilian clothes when security screening at Yakima (Wash.) Air Terminal revealed the grenades in his carry-on bag, the Yakima Herald Republic reported Monday.

The incident Sunday morning triggered an evacuation of the Yakima airport while U.S. Army bomb specialists dismantled the grenades. Several flights were delayed.

The man, who was headed to Seattle, was released after questioning but the Herald Republic said he could face charges by Yakima County prosecutors as well as questioning by the FBI or Transportation Security Administration.

Investigators said the man was planning to return to his base in California. They said they didn't know why he was in the Yakima area, the newspaper reported.

Training grenades can cause injury when detonated even though they contain no explosives.