Police in Selby are appealing for witnesses and information after a flare was set off in Poundland on Abbey Walk at around 3.30pm on Tuesday 19 September 2023.
It filled the store with orange smoke which caused distress to several elderly shoppers who were evacuated coughing and choking.
Poundland estimate the disruption cost them £600 in lost sales.
Following enquiries, two boys aged 17 and 16 have been arrested in connection with the investigation.
Police are carrying out a search for another teenage boy who is believed to have been in the store at the time.
If you witnessed the incident or were one of the shoppers who had to be evacuated due to coughing and choking, please email ben.pepper@northyorkshire.police.uk or call 101, option 2, and ask for Ben Pepper.
If you would prefer to remain anonymous, you can still help by contacting Crimestoppers on 0800 555 111 or make an online report.
Please quote reference number 12230177881 when providing details.