Two people were taken to hospital after a CS gas was reportedly set off in a Kidderminster nightclub.
It happened at Nu Bar just after 1am this morning.
Four people were assessed by paramedics and two were taken to A&E but have since been released.
A 29-year-old man was arrested on suspicion of possessing a weapon for the discharge of a noxious liquid or gas and assault ABH. He remains in police custody at this time.
The investigations are currently ongoing and anyone with information about the incident or who was in the area at the time is asked to contact West Mercia Police or Crimestoppers anonymously.