Police last night opened an arson investigation into a fire that caused minor damage to a Makiki business unit at 1344 Young St.

Honolulu Fire Department Capt. Earle Kealoha said the 8:45 p.m. fire was started by a plastic bag thrown over a wall at the unit which exploded into flames. Damage to the unit was contained to a patio-type area, Kealoha said.

Police have made no arrests.