Teenagers were rushed to hospital after an unknown substance was thrown at them by a man in the street.
The incident happened on Common Lane in Warrington, at around 9.40pm on Friday, October 11.
It is not known how many youths were involved but they were taken to hospital, where they received treatment, but have since been discharged.
The extent of their injuries is not known.
Cheshire Police said the man involved had left the scene before officers arrived but today, detectives appealed for help tracking down a man whose picture they released to the media.
Police are urging anyone who recognises him or thinks they may know who he is to get in touch.
Sergeant Neil Bradley, of Warrington Local Policing Unit, said: “I would like to reassure the community that this is believed to have been an isolated incident.
“Thankfully none of the teenagers sustained any serious injuries as a result of the incident and enquiries are ongoing to establish exactly took place.
“We believe that the man in the image may have vital information to help with our enquiries.
“If you think you recognise the man or know who he is please call Cheshire Constabulary on 101, quoting IML 536699, give us the details via https://www.cheshire.police.uk/contact/general-enquiries or contact Crimestoppers anonymously on 0800 555 111.
“I would also like to appeal directly to the man in the image to get in touch.”
