The teenagers, four youths and a girl, aged 14 and 15 were approached by the ‘detective’ at Lower Church Road, Raheen.
He told them he was investigating illegal possession of fireworks and ordered all five to stand facing a wall.
He frisked all the boys and told the girl he could not frisk her as he was not accompanied by a female garda.
After searching the boys, he ordered them to hand over their mobile phones as the gardaí needed to scan them for information as part of their investigation into illegal fireworks.
Before he returned to his parked car he warned the group to remain facing the wall and not to move until he returned.
The father of one of the boys, who asked not to be named, said: “It was a bizarre incident. They were all fairly shaken by the experience. The fellow pretending to be the detective, while he did not hit anyone, was very intimidating. The fact that he physically laid hands on them meant there were assaults; I and other parents contacted Roxboro Garda Station who came back to us informing us that an investigation was under way and they said they will keep us informed.”
Det Sgt Denis Treacy said the incident happened at around 4.30pm on Friday last.
He said: “This individual confronted the group of teenagers after he pulled up in a car and got out. After searching them, he took their mobile phones. This man was not a member of An Garda Siochána.
“From the descriptions we got, he was a big man in his 20s or 30s. He was wearing a Superman T-shirt. After searching the group and taking their mobile phones he drove off.
“This was a frightening experience for the youths and the girl. We would like to hear from anybody who may have been at Lower Church Road, Raheen, last Friday afternoon and may have seen the incident, or from anybody who may be able to help.”
Contact gardaí on 061 214340.