The memorial was discovered cut-down on Wednesday at the Firemen’s Memorial Park in Washingtonville, New York.
Mayor Joseph Bucco, who alerted Washingtoville police to the attack, wrote on Facebook that the “police department is in the process of collecting evidence, and I promise you they will not leave any stone unturned to find the person or people responsible for these damages.”
Mr Bucco said Washingtonville’s police department launched an investigation alongside New York State’s public works department, who have since appealed for anyone with information to come forward.
“When everyone arrived at the site, we noticed that this flagpole was cut down using some type of saw,” said the mayor. “There was some graffiti on the part of the flagpole still intact.”
“We also learned the entrance sign to Saint Mary’s Parish Center was also destroyed and the eagle that stood on the Memorial Flagpole was seen at the Saint Mary’s Site,” he added.
Pictures shared online showed the severed pole cut near the base, where police said vandals had scrawled a message.
“It was really just devastating to see that somebody could be that depraved to go in and destroy and deface a memorial to the Washingtonville five,” said New York Assemblyman Colin Schmitt to Fox News.
“Five brave men, who everyone remembers sacrificed their lives fighting terror on our own soil,” added Mr Schmitt, referring to the New York City Fire Department personnel who lost their lives on 9/11: Mark Whitford, Bobby Hamilton and Gerry Nevins, Batallion Chief Dennis Devlin and Lt. Glenn Perry.
Washingtonville’s mayor added on Wednesday that authorities will restore the memorial, whilst a $3,000 (£2,372) reward is on offer for providing more information about the incident.