Sussex Police has announced its theory of how a fire at a block of flats which killed two puppies was started.
The force is appealing for witnesses to the fire at Ganymede Court, Bewbush, Crawley, which broke out at about 4.10am on Sunday (14 July).
Two puppies die and dozens without power in serious Crawley flat fire
Residents were evacuated while West Sussex Fire and Rescue brought the fire under control, and one woman was taken to hospital with suspected smoke inhalation, police said.
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.