Gardai are investigating the circumstances surrounding a video uploaded on to a porn website that allegedly showed a man and woman engaged in a sex act on a squad car.
The man is believed to be wearing a jacket similar to those worn by gardai in the course of their duties.
Handcuffs can also be seen in the footage.
In the clip, which lasts just under five minutes, the couple hold up a copy of an Irish tabloid newspaper from last Saturday in which it was reported that a woman was filmed engaged in a sexual act with members of the Defence Forces.
It is believed the same woman appears in both videos. The footage is understood to have been filmed in the southwest of the country.
The man and woman are heard talking on the video and the woman has an English accent.
Her face can be seen but the man's is not visible. The woman is not believed to be a garda and it is not known if the man is a serving officer.
An internal investigation was launched after the video was uploaded over the weekend.
A garda spokesman said it was aware of the video but it is not making any comment.
However, the Herald understands a full internal investigation is now under way in a bid to establish the origins of the tape and how a squad car, garda jacket and handcuffs appeared in the video.
Since it was posted online, it has been viewed thousands of times.
"It would appear to be a proper garda raid jacket, proper handcuffs and a legitimate squad car," a source said.
"Early indications are that this was in the south west of the country."
It is the latest in a number of recent scandals to rock An Garda Siochana.