Young children playing at a caravan site where a seven-year-old boy was knocked down and killed by a car may be vital witnesses to what happened.
Police appealed to their parents to make contact as a teenager arrested on suspicion of causing death by dangerous driving remained in custody.
A 16-year-old boy was allegedly driving the BMW car involved in the accident at Shirenewton caravan site, east of Cardiff, South Wales.
He was arrested soon after the incident at 3pm on Saturday and is still being questioned by South Wales Police.
The seven-year-old boy, who has not been named, is from the caravan site and was "apparently in collision with a red BMW 3rd series estate", police said.
He died from injuries sustained in the accident after being taken to hospital. Specially trained police officers are with his family.
South Wales Police made a fresh appeal for any witnesses to the accident to come forward.
A police spokeswoman has now revealed that children playing at the time of the accident may be key witnesses to the tragedy.
"It is believed a group of children and young people may have witnessed the collision and officers are urging them and their parents to make contact," she said.
"They might have important information to assist the investigation and would also be offered any support they might need."