The fire at Enys Road, Eastbourne has now been extinguished.
ESFRS was called to attend the incident at the residential property at 1.25pm. Eight fire engines were in attendance and one aerial ladder platform, four breathing apparatus, one main jet and 1 in 7 foam were used.
All residents were safely evacuated and one person with smoke inhalation was left in the care of SECAmb.
It was an electrical fire that started in the basement of the property. A fire investigation is being undertaken.