Eight cars and a garage door were tagged with gang-related graffiti overnight on several streets in Coram.
Suffolk Police Commissioner Tim Sini said that the group responsible for the graffiti is "not one of the larger gangs in Suffolk County, but we take it very seriously."
News 12 Long Island is choosing not to name the gang involved with the incident.
Authorities are urging anyone with information about the incidents to call the police.
Police said windows were also broken on six vehicles in neighboring Farmingville. They said they do not believe the incidents are related.