Paramedics and police were called to part of the Nutbrook Trail as it passes beneath Ladywood Road up towards Ilkeston, at about 9.20pm on Saturday 8 May.
A 17-year-old boy was found injured and was taken for treatment to Queen’s Medical Centre in Nottingham, where he remains.
Two boys aged 14 and 15, and a 19-year-old man, have this evening been arrested in connection with the alleged assault.
Detective Inspector Steve Bruce, who is overseeing the investigation this evening, said: “I appreciate that this incident may cause alarm in the local community but I would like to reassure people that we believe it to be isolated.
“We are in the early stages of our investigation and have a number of people we want to speak to in relation to it.
“That work will continue into the night and I would urge witnesses or anyone who can help us with it, to get in touch.”
Anyone who can help should contact us using one of the below methods, quoting reference 20*253955.
• Facebook – send us a private message to /DerbyshireConstabulary
• Twitter – direct message our contact centre on @DerPolContact
• Website – complete the online contact form https://bit.ly/2a5L5jj.
• Phone – call us on 101.
You can also give information anonymously to the independent charity Crimestoppers, by calling 0800 555 111.