Investigators searched for those responsible after fire broke out inside a deli in the Wissinoming section of Philadelphia.
Firefighters were called to Romano's Grocery and Deli at the intersection of Carver Street and Torresdale Avenue around 4 a.m. Sunday.
Investigators said an unknown substance was thrown into a vacant apartment above the deli which caught fire.
No injuries were reported.
The fire marshal investigated the blaze as suspicious.
