Two people were injured when a firework exploded in a crowd of spectators in the West Midlands on Friday.
Both suffered minor leg and chest injuries, and two children were assessed at the scene at the fireworks display in Broadway, Worcester, at around 7pm.
It is believed that five others may have been hurt, but all had left before emergency services arrived.
A West Midlands Ambulance Service spokesman said: "Crews responded to a firework incident at a public event in Childswickham Road.
"Two adults presented with minor leg and chest injuries and two children were assessed at the scene.
"It is understood at least five other people received minor injuries but left the scene before the emergency services arrived.
"All the patients were treated at the scene and later released."
Earlier this week, the London Fire Brigade urged people to cancel plans to hold their own firework displays ahead of Friday's strike over government plans to increase the age at which they can retire to 60.
Each year, the UK celebrates Guy Fawkes's failed attempt to blow up the Houses of Parliament in 1605 by burning an effigy of the plotter on a bonfire, and with firework displays.
London Fire Commissioner Ron Dobson said: "Fireworks cause serious fires each year and bonfires can quickly get out of control, which is why we're urging people to attend organised displays.
"During the strike we will have a contingency fire and rescue service of 27 fire engines, crewed by temporary firefighters.
"Serious emergencies will be attended, but smaller incidents won't so we are calling on the public not to put themselves at risk by lighting fireworks and bonfires."
A second strike is planned for Monday 4 November, the eve of Bonfire Night.