Four metal sluice gates, belonging to the Environment Agency, have been stolen in Derby.
The gates weigh around nine tonnes in total and were stolen sometime between May 18th and May 22th.
The gates had been stored beside a bridge that spans the river near the new A6 bypass at the back of the Celanese plant, Spondon.
Police believe the thieves would have needed specialist equipment to steal the gates and they would have been at the site for some time removing them.
Scrap merchants in Derbyshire have been warned about the theft in case the thieves try to cash the gates in.