This was the third blaze in two weeks at the same vacant apartment building on Corporate.
It caught fire again around 10pm and destroyed the second floor and roof.
The building had been boarded up since the first fire two weeks ago.
Authorities say the flames last night were so intense they had to pull a second alarm. According to investigators, they became suspicious about the cause because the fire had several different points of origin.
Arson investigators are looking into the fires.