Fans even hired an airplane to fly over the stadium with a banner that said, "Respect for Nocera and the ultras."
Nocerina's "ultra" fans issued a statement Monday saying that they did not issue any death threats. Rather, they said they only wanted to issue an "unmistakable message" and "give voice to an unfair act imposed on the fans."
Nearly 9,000 fans attended the match and some asked for their money back.
The area near Naples where the two clubs are from is infested by the Camorra crime syndicate.
There have been calls for Nocerina to be kicked out of the league, which is known as Lega Pro.
Italian football has been marred by racism, territorial chants and fan violence for years. Already this season, a handful of Serie A clubs have had portions of their stadiums closed due to fan misbehavior.
"We're the laughing stock of the entire world," Italian Olympic Committee president Giovanni Malago said, adding that the neighboring clubs should not have been placed in the same division.
Italian football federation president Giancarlo Abete added that the incident should prompt "serious reflection on how to prevent these situations."