WINDHAM, Me. — Mike Barrett, a corrections officer, ripped open an envelope in the mail room at the Maine Correctional Center here and eyed something suspicious: a Father’s Day card, sent a month early. He carefully felt the card and slit it open, looking for a substance that has made mail call here a different experience of late.

Mr. Barrett and other prison officials nationwide are searching their facilities, mail and visitors for Suboxone, a drug used as a treatment for opiate addiction that has become coveted as contraband. Innovative smugglers have turned crushed Suboxone pills into a paste and spread it under stamps or over children’s artwork, including pages from a princess coloring book found in a New Jersey jail.

The drug also comes in thin strips, which dissolve under the tongue, that smugglers have tucked behind envelope seams and stamps.

“It’s become a crisis in here, to be honest with you,” said Maj. Francine Breton, administrator of the Cumberland County Jail in Portland, Me. “It’s the drug of choice right now.”