Authorities say federal transportation agents found the items Monday when the man and his 4-year-old went through security at T.F. Green Airport. The man said he didn't know the items were there.
An airport spokeswoman says he was detained for three hours and let go. He continued traveling Tuesday.
Airport officials released a statement Wednesday calling it a "domestic custody dispute."
Airport police, state police and the FBI are investigating.
The Transportation Security Administration and FBI declined to comment Wednesday. State police referred questions to airport police. Airport Police Chief Leo Messier didn't immediately return a message Wednesday.