Police were called to reports of a disturbance at a property on Grand Parade, Brighton at around 11pm, a spokesperson said. Further information suggested a chemical incident, reportedly related to ammonia, had taken place inside the address.
"Fire and ambulance service crews attended the scene alongside police to support the evacuation of the building, and a temporary road closure was put in place between the junctions of Richmond Parade and Morley Street as a safety precaution,” the spokesperson added.
"Two men and a woman, who are all known to each other, were arrested in connection with the incident and taken to hospital for treatment.
“One of them – a 32-year-old man from Brighton – has since been discharged. He was arrested on suspicion of causing grievous bodily harm with intent, criminal damage and assault of an emergency worker. He remains in custody at this time.”
The other two are still in hospital, according to police, and their injuries are not believed to be serious.
The area has been made safe by emergency service crews and there is not believed to be any wider risk to the public. Anyone with information about what happened is asked to contact police online or by calling 101 quoting serial 1526 of 23/08.