Westfield Mayor Shelley Brindle said 11 cases announced Saturday were in the age group of 18 to 25.
Three of those cases were traced to attendance at parties while the others remain under investigation.
RELATED | 7 On Your Side Investigates: Up to 4,000 coronavirus cases prevented by NYC contact tracers
Up to 4,000 COVID cases prevented by NYC contact tracers: officials
Brindle said parents and families should reconsider hosting or attending graduation parties.
She asked anyone who thinks they were exposed to get tested and start self-quarantining for 14 days.
"I hope this spike serves as a reminder that we all have a responsibility to remain vigilant to mitigate community spread," Brindle said in a Facebook post. "Wash your hands. Keep a safe distance. Wear a face covering. Working together, we can get this genie back in the bottle."
Officials in New York are also monitoring an uptick in cases in Rennselaer County after several individuals traveled back to New York from Georgia.
WATCH EYEWITNESS TO A PANDEMIC (Episode 4)
Eyewitness to a Pandemic: Episode 4 - The Apex
[Ads /]
MORE CORONAVIRUS COVID-19 COVERAGE
abc7NY Phase Tracker:
COVID-19 Help, Information. Stimulus and Business Updates
UPDATES
New York City
[Ads /]
New Jersey
Long Island
Westchester and Hudson Valley
Connecticut
REOPENING INFORMATION
What's Open, What's Closed
[Ads /]
Reopening New York State
Reopening New Jersey
Reopening Connecticut
How to prevent 'Mask-Ne' aka Mask Acne
Coronavirus pandemic causing new skin issue: 'Mask-Ne' aka Mask Acne
Total count of NYC, Long Island COVID-19 cases based on patient address