Police are appealing for witnesses to a deliberate fire in a block of flats at Ganymede Court, Bewbush, Crawley, which broke out at about 4.10am on Sunday (14 July).
Residents were evacuated while West Sussex Fire and Rescue brought the fire under control. One woman was taken to hospital with suspected smoke inhalation. Two flats were badly damaged in the blaze.
Detective Inspector Pauline Lane said: "We are treating this fire as a deliberate act and we would like to hear from anyone who witnessed the fire being started or saw anyone acting suspiciously in the area."
Any witnesses to the incident or anyone with information should report online or ring 101 quoting Operation Clayhill.