A schoolboy was taken to hospital after he was bitten by a police dog as armed officers responded to a machete alert.
It came as armed police and a dog handler rushed to the area after a man dialled 999 to say he had been chased by a group brandishing machetes.
West Midlands Police has referred the incident, which happened at 8.20pm on Tuesday 11 October, to the Independent Office for Police Conduct (IOPC).
The extent of the teenager's injuries was not known but an ambulance was called.
The 14-year-old was arrested on suspicion of affray and remained on police bail as enquiries continue.
Three other boys, aged 17, and an 18-year-old man were arrested on suspicion of a public order offence and released on police bail pending further enquiries.
A spokesperson for West Midlands Police said: "We were called to Finchley Road, Birmingham, at 8.20pm on Tuesday 11 October by a man saying he'd been chased by a group brandishing machetes.
"Armed police and a dog handler responded and a police dog was deployed after the group ran off. A 14-year-old was bitten a police dog as we attempted to detain him.
"An ambulance was immediately called, but officers drove him to hospital themselves to ensure he got swift medical attention. The 14-year-old was arrested at the scene and remains on police bail as enquiries continue.
"Our Professional Standards Department has referred the matter to the IOPC.
"Three other boys aged 17 and an 18-year-old man were arrested on suspicion of a public order offence and released on police bail pending further enquiries."