Police are appealing for witnesses after yobs lit a firework and threw it into a store in Dewsbury.
The incident happened around 5.30pm on Tuesday - Halloween night - at the Boots store in Princess of Wales shopping centre in Dewsbury town centre .
Witnesses told how the firework was thrown by a youth and went under shelving and then exploded.
No-one was injured and no apparent damage was caused to the store.
A West Yorkshire Police spokesman confirmed officers attended and enquiries are now ongoing to trace two male suspects, one of whom was described as wearing black Adidas bottoms and carrying a yellow shoulder bag.
Anyone who has information or who witnessed the incident should contact the Dewsbury and Mirfield Neighbourhood Policing Team on 101 referencing log 1433 of October 31.