The New London State’s Attorney Office will not open a criminal probe into the city’s private investigation into its Public Works Department.

In a memo presented to the City Council Monday night, State’s Attorney Michael L. Regan said he had analyzed the roughly 500 pages of employee-interview transcripts, which he had requested in late January from New London Police Chief Bruce Rinehart.

“I do not believe further investigation by our office is warranted,” Regan wrote in his Feb. 20 letter to Rinehart.

“The questions raised by the report mainly relate to labor-management issues. The allegations of criminal conduct are unsubstantiated and appear to be beyond the statute of limitations,” Regan wrote.

Rinehart said he also reviewed the report and agreed with Regan’s analysis, according to a Feb. 26 memorandum Rinehart sent to City Manager Martin H. Berliner.

In the report, which was based on 34 voluntary interviews, public works employees told investigators of on-the-job marijuana use by supervisors, according to a six-page summary of the interviews. City attorneys have declined to release the full report.

Employees also alleged that the department’s second-in-command, who retired in the fall and whose position the city has eliminated, installed a plow on his city truck for personal use and disposed of debris from a private business on city time at the transfer station.

The report’s allegations of illegal activity were among numerous and often contradictory employee complaints, which included mismanagement, delayed city projects and extremely low morale in the city’s second-largest department.

The interviews for the $14,000 investigation, which was conducted by Countermeasures Investigations/Surveillance LLC of Wethersfield, occurred this past summer. The firm’s findings were delivered to city officials around August.