MILLBROOK — Officials at the Tri-County Regional Library confirmed Tuesday that the Quiet Study Wing has grown so silent that at least four patrons have been declared missing, prompting a search party that is legally and morally prohibited from shouting.

“We first noticed something was wrong when a man’s sandwich was still on his desk after three days,” said Library Director Marguerite Oyelaran-Finch, speaking in a low murmur from the circulation desk. “Normally you can hear someone sigh from forty feet away. We heard nothing. That’s when we knew.”

The wing, which was designated “Quiet” in 1994 and upgraded to “Very Quiet” in 2009, was recently reclassified as “Silent, Please, We Mean It” after a patron reported hearing a thought. Staff say the silence has since deepened to the point that sound itself appears to be avoiding the room.

The search party, composed of eleven volunteers and one retired school librarian, entered the wing at 9:15 a.m. wearing felt-soled slippers and carrying flashlights wrapped in tissue paper. Under library rules, members may communicate only by whisper, and no name may be spoken above what Oyelaran-Finch described as “a decorous hiss.”

“We’re calling for them as loudly as we’re allowed,” said Dr. Phineas Aldous Trembley-Wu, a certified Acoustic Retrieval Consultant at the Institute for Applied Hush at a community college two counties over. “Right now that’s a sort of breathy ‘Gary?’ It carries about as far as a moth.”

Trembley-Wu said the search is complicated by the fact that missing patrons may be unable to answer back. “If they’re anywhere near the Large Print Biographies, they’ve almost certainly been shushed into a kind of stillness,” he said. “It’s a survival tactic. The shelves have seen things.”

“We’re calling for them as loudly as we’re allowed. Right now that’s a sort of breathy ‘Gary?’ It carries about as far as a moth.”

Early progress has been slow. Searchers reported finding a cardigan, a half-finished crossword, and a single pencil that was “sitting there in a manner I can only describe as respectful.” At 11:40 a.m., a volunteer thought she heard a faint rustle near Periodicals, but it was later determined to be a page being turned by a man who had been reading the same issue of Modern Beekeeping since Saturday and had simply not looked up.

“Oh, I’m fine,” said the man, identified only as Delbert, in a voice so soft that three searchers asked him to repeat it. “I thought it was just a really good silence.”

The library has taken steps to prevent further disappearances, including posting a sign reading PLEASE REMAIN AUDIBLE and issuing each patron a small bell. The bells were collected within an hour after a staff member found them “disruptive.”

At press time, the search party had located one patron, who was found in the Reference section and declined to be rescued, citing a nearly finished chapter. Three remain unaccounted for, and Oyelaran-Finch said the library will continue the search until closing, at which point she will ask everyone to leave, quietly.

“If you’re in there, please come forward,” she whispered. “Or don’t. Honestly, we’ll respect either.”