Police have denied claims they were heavy-handed during a riot in which 70 people attacked officers close to Londonderry's City Cemetery.
Youths were involved in the rioting
It happened as officers tried to speak to organisers of what is believed to have been an illegal dissident republican parade in the area.
An eyewitness said police photographed and questioned children.
PSNI Inspector Trevor McKeown said it was a known procedure for evidence to be gathered by way of photographs.
However, he said he was not aware that young children were involved in the investigation.
"Certainly we were not being heavy-handed. We were noting names and we were gathering evidence of what exactly was going on," he said.
"I think that rather than being heavy-handed, we did quite a good job in being able to get 41 petrol bombs off the ground... petrol bombs are lethal weapons - they can kill somebody and burn property.
"People can fire them at us, and not necessarily hit us, but hit a house or hit a child instead."
A police vehicle came under sustained attack from people throwing petrol bombs, bottles and containers of paint.
Police recovered 40 petrol bombs following the trouble which started at about 1500 GMT on Monday.
There were no reports of any injuries. Two teenagers who were arrested have been released pending reports to the Public Prosecution Service.