Investigators say Monday's fire originated inside a third floor apartment at the Village of Canterbury complex.
A 51-year-old man remains hospitalized in critical condition.
Damage is estimated at $1 million.
The Red Cross is assisting more than 20 displaced residents.
Firefighters were hampered fighting the blaze because of a gas line that ruptured and ignited. The heat from the impact also caused an air conditioner to explode.
A total of 12 units were destroyed.