A 12-year-old boy has died after falling through the roof of a derelict factory.
The boy , who has been named as Adam Johnson, was with two friends at the Aida Bliss building in City Road, Chester Green, when the accident happened on Friday (8 September).
Arriving at the scene, emergency services found him critically injured and he was taken to hospital, however he was later pronounced dead.
Officers believe another group of youngsters were also in the factory and have appealed for any witnesses to speak to them "urgently".
Ch Supt Jim Allen, of Derbyshire Police, said: "This is a tragic incident and our thoughts and sympathies go out to the young boy's family.
"If you were in the building at the time, you will not be in any trouble - we just need to speak to you as a witness as soon as possible, so please call us now."
Adam's mother Kerry, 47, was devastated by his loss. "I'm overwhelmed with emotion. I can't believe he has gone," she told Mail Online. "I can't say anything else at the moment."
Specially trained officers and staff are supporting the boy's family "at this unimaginably difficult time" BBC News reports.
Police said the boy's friends who witnessed the accident have also been left "understandably distraught" by the tragedy.
The 19th century building was once used to make metal stamping presses, but closed in 2004. Children often go into the abandoned building to take photos and videos to post online. Local residents claimed the building was a 'death trap' and have been urging the local council to secure the factory to prevent children climbing onto the roof.