Fayetteville, N.C. — A Fayetteville apartment fire that left 21 people without a home Wednesday evening was intentional, fire investigators said Thursday.

Sixteen adults and five children living at the Village at Cliffdale Apartments, at 575 Cutchen Lane, were displaced after the fire, which broke out in a ground-floor bedroom around 5:45 p.m. Wednesday.

The majority of fire damage was contained to the apartment, but damage did extend to the entire building.

Authorities did not say what led them to conclude the blaze was intentional but said the State Bureau of Investigation and Fayetteville police are now involved in the case.

It's still unclear what caused a second apartment fire about 30 minutes later at Crossings at Morganton, on Waterdown Drive, investigators said.

Fire crews found heavy fire on the second- and third-floor balconies when they arrived. Witnesses reported hearing a loud noise, or "pop," prior to the fire, investigators said.

The SBI is also assisting in that case, in which 18 people were left homeless.

The American Red Cross is assisting those affected by the fires.