MINNEAPOLIS (AP) — Investigators say they cannot determine what caused an explosion and fire that damaged a building housing four apartments in south Minneapolis.

According to the Minneapolis Arson Unit, the fire originated in the living room of a first-floor unit. But fire officials say the cause is considered to be undetermined.

Authorities say nobody was home when the explosion occurred Tuesday afternoon. But, a dog was killed in the blast.

One tenant, Rob Ayott,says he lost everything he owns in the fire, including his artwork, violin and collection of action figures.

CenterPoint Energy worked with fire investigators on a possible cause.