Cannabis plants were found in a house which was ravaged by fire last night.
The blaze damaged the roof and top floor of the house in St Aubyns Road, Fishersgate, on Wednesday (July 4) night.
A 27-year-old man was arrested on suspicion of arson. He was being questioned in custody today.
Sussex Police said they found a small number of cannabis plants but no-one has been arrested over the drugs.
Firefighters confirmed 75% of the first floor and 100% of the roof was damaged by fire and heat.
People living in the flat below were told it was unsafe for them to go back in today.