Officers are investigating a report of an attempted robbery in Thornaby on Thursday 23rd November.
The incident happened around 12:05am on Teesdale Terrace, when a man reported being attacked by four males who demanded his property and hit him with a hammer before making off.
The 31-year-old man suffered a wound to his head and was treated in hospital overnight.
Enquiries are ongoing identify those involved.
Police are appealing to anyone who may have witnessed the incident or anyone who may have dash cam footage of the incident is asked to contact Stockton CID on the non-emergency number 101, quoting incident number 232219.
Independent charity Crimestoppers can be contacted anonymously online at www.crimestoppers-uk.org or by calling 0800 555 111.