The occupants were located and confirmed safe but it was not known if they were present at the time of the fire, he said.
Because one person left the property shortly before the fire "and the circumstances surrounding the incident" he said the fire was being treated as suspicious.
An immediate neighbour who declined to be named said she was awake when she heard "a very loud bang".
She went outside where she saw large flames and dialled 111.
She then helped several female seasonal fruit workers to climb their shared fence so they would be safe on her property.
Donna Keeley lives three doors down and was woken by her dogs' barking.
"As soon as I opened my door I saw a red glow and my heart sank," she said.
"By the time I got to my drive I could already hear the hissing and popping. Most of my neighbours were already outside.
"There was a sound of a car's wheel's screeching before the bang so everybody thought there had been a really bad accident."
Another neighbour said she woke to "a large rumble explosion sound".
"At first I thought it was an earthquake but it didn't follow with shaking," she said.
"I looked out the window and noticed the flames a few doors down, by the time we got there the police had just turned up and it was well alight."
The owner of the destroyed property, Jim Lowe, said everyone was safe and accounted for.
He said the front flat was occupied by four people: a couple and child and the woman's grandmother.
"I got a ring this morning saying there was a fire here and when I arrived fire crews were obviously putting the fire out and making sure nobody was still in the building," he said.
"They have spoken by phone with all of the people that were there and all are safe.
"They weren't home at the time of the fire apparently."
He said he used the large shed for storage and did not think it was the seat of the fire.
"The fire investigator will find out that it appears, looking at this, that the fire was in the flat and spread to the shed."