Police and firefighters were called to a high street in Leeds after a report of a loud explosion this morning.
The explosion happened in the area around a bin outside Greggs on Town Street, Armley.
A police spokesman said: "Enquiries between the joint emergency services have shown a firework was placed in the bin.
"No damage was caused, however, it is understood the event may have caused alarm to people in the area."
Now officers want to hear from anyone who witnessed the explosion or may be able to help to identify the person responsible.
He is described as a white man, aged in his late 30s and 5ft 10in.
The man wore a dark blue t-shirt and blue gilet, and had stubble on his face.
Anyone with information is asked to email firstname.lastname@example.org or call the Leeds Inner West team on 101, quoting reference 13170438218.