Fire at Southsea flats on Saturday morning
More than 40 firefighters were called to tackle a blaze in a basement flat which quickly spread to properties above.
Fire engines from Cosham, Havant, Southsea and Portchester were on scene, along with a command support vehicle from Eastleigh.
The fire in South Parade, Southsea sent up a large plume of smoke, prompting multiple 999 calls.
Crews wore breathing apparatus and used four jets and three hose reels to surround the fire and dampen down.
Three casualties were treated for smoke inhalation with one casualty led to safety by firefighters before being passed to South Central Ambulance Service paramedics.
A cat was also rescued from the building and treated for smoke inhalation before being handed into the care of the RSPCA.
The stop message came in shortly before 11:22am with one crew returning later that evening to conduct a reinspection and check for further hotspots.
The incident is now under investigation to ascertain the cause.