Investigators are trying to determine what caused a blaze at a Freeport deli.Neighbors say they heard an explosion around 3 a.m. and then saw flames shooting out the front of the store. The fire spread to a liquor store and another store that received minor damage. One firefighter was injured battling the blaze.The deli was raided weeks ago as part of an investigation into an alleged poker machine gambling ring. Police say machines were removed from the deli.