A 15-year-old boy is in hospital undergoing treatment after a firework exploded in his hand.
The youngster was taken to North Tees General Hospital following the accident on Wednesday morning, but his injuries are not thought to be serious, police said.
Officers are now urging the public to make sure fireworks do not fall into the hands of under-age youngsters.
It is illegal to sell fireworks to anyone under the age of 18.
Inspector Mick Knapper of Cleveland Police said: "Our thoughts are with the boy and his family in the hope of a speedy recovery.
"Fireworks are explosives and burn at high temperatures, so they need careful handling and storage; they are not toys to play with.
"They should not be lit by young people, adults should light them at arms length with a taper, and stand well back once lit."