Four men have been arrested after white powder was thrown at people in apparently racist attacks across a city, police said.
The victims, the majority of whom were black, were targeted in a number of incidents in north Manchester on Monday, according to Greater Manchester Police.
The four men were arrested on suspicion of causing grievous bodily harm with intent and remain in police custody.
Officers were called to Jersey Street in the city following reports of someone coming into contact with an unknown substance. Another person went to North Manchester General Hospital shortly afterwards with a similar report.
Police received a further report from a man having a white powder thrown at his car in Blueberry Avenue.
Greater Manchester Police said it worked very closely with Greater Manchester Fire and Rescue Service following the incident.
It has now been confirmed that the powder was non-hazardous.
Detective Inspector Alex Nicholson said: "We believe there are other victims out there who have had powder thrown on to them. While it is important they seek medical advice, it is equally important they call the police.
"The vast majority of victims were black men and we are treating this as a racially-aggravated series of attacks."
Anyone with information is asked to call police on 0161 856 3540 or call the independent charity Crimestoppers anonymously on 0800 555 111.