A rower has been injured after being hit by a firework thrown by a group of young people on Ormeau Bridge in south Belfast.
Police said a rowing boat sustained significant damage in the incident on Tuesday evening.
A group matching the description was approached by officers and a small amount of fireworks were recovered.
Police said a 12-year-old boy was also taken home and cautioned in front of his parents.
He will be referred to a youth diversion officer.
Ch Insp Gavin Kirkpatrick said the misuse of fireworks is "an extremely reckless act, which can result in serious harm and life changing injuries".
"This irresponsible action not only threatened the life of the people using boats on the river, but also of the person throwing the fireworks and those who were also present at that time.
"It is illegal to possess, sell, handle or use fireworks if you do not have a licence and if detected, you can be fined up to £5,000 for breaking the law."