A top Clackamas County sheriff's supervisor was placed on paid administrative leave this week amid allegations that male deputies staged a nude photoshoot at the courthouse after hours for a calendar they gave to a retiring colleague.

The Sheriff's Office will launch an internal investigation, officials said Friday.

The allegations were contained in an anonymous letter addressed to Sheriff Craig Roberts and also mailed to The Oregonian/OregonLive.

The letter writer said the calendar contains photos that include nude deputies with objects hiding their genitals, including a gun belt and a firefighter's hat, another nude deputy on a desk with his backside facing the camera and shirtless deputies posing in a flower bed, on the second floor of the courthouse, and with an assault rifle and a cat.

Capt. Dave O'Shaughnessy, a 24-year veteran with the Sheriff's Office who heads the civil division, is now on leave, said Deputy Ben Frazier, an agency spokesman. O'Shaughnessy supervises courthouse deputies, among other duties.

The allegations are being taken "very seriously" and employees will be held accountable if any laws or policies are determined to have been violated, the sheriff said.

"Behavior like this, if true, is not acceptable and extremely troubling," Roberts said.

KPTV first reported the investigation.

The unsigned, typed letter said the calendar was meant to mock gay men. The letter writer didn't identify himself but said his wife, a state worker, told him a courthouse deputy "was laughing and bragging to her" about the calendar last week.

The letter does not name any of those involved, but said a commander, supervisor and deputies were among those who took part in the photoshoot. The photos were taken on a Saturday in and around the county courthouse in Oregon City, the letter said.

The calendar was presented to the retiring deputy at the end of the retirement party by a sheriff's office commander to prevent another supervisor from finding out about it, the letter said.

-- Everton Bailey Jr.

ebailey@oregonian.com

503-221-8343; @EvertonBailey