Security personnel found the first magazine "stashed on the racks between the goods" on Thursday and turned it over to police, law enforcement source with direct knowledge of the incident told Daily Voice.
"Another was found today and left in place," the source said.
The store was cleared for a search by a K-9 unit from the Bergen County Sheriff's Office.
The sheriff's Bureau of Criminal Identification took custody of the magazines and collected evidence.
Detectives were reviewing store surveillance images.
A magazine is slid into the bottom of a handgun and holds shells under spring pressure that are fed into the weapon's chamber.
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