Troopers responded to City Hall Tuesday to gather evidence.
Officials say the matter was referred to the Attorney General's Office by the City approximately two years ago.
"The investigation concerns a matter that the City itself identified, investigated, and referred to the New Jersey Attorney General's Office approximately two years ago," Trenton Mayor W. Reed Gusciora said in a statement.
The investigation stemmed from 2024 allegations concerning an employee of the city's Housing and Economic Development Department, according to a statement from city officials, but would not comment further on the investigation.
"This Administration has zero tolerance for misconduct or violations of the public trust," Gusciora said. "When credible allegations of wrongdoing come to our attention, we investigate them and, where appropriate, refer the matter to the proper law enforcement authorities. That is exactly what the City did here."
The city is fully cooperating with the investigation as it progresses, according to officials.