Two security guards were assaulted by an armed gang attempting to steal from the site of a new Nottingham school.
The incident occurred at the site of Retford Oaks School on Babworth Road in Retford on Thursday night.
Two men carrying weapons attacked the guards before detaining them, while accomplices made attempts to steal property from the site.
One of the guards, aged 32, required hospital treatment, but was released a short time later.
It is believed the accomplices were driving vehicles, which were possibly Transit-style vans or flat back lorries.
Det Sgt John Bird, who is investigating the incident, said: "The security staff are local men who were doing their job protecting the new school facility being built for our children.
"I believe someone within our community will have information or knowledge of the offenders and I would appeal to them to come forward."