A total of 73 TTC employees have been fired so far as a result of an ongoing investigation into an alleged insurance fraud scheme, the TTC announced Thursday.

The investigation began in 2015, after allegations surfaced through the TTC’s whistleblower program. Some 600 employees are being investigated for involvement in the scandal, the city’s auditor general said last year.

The allegations centre on a local orthotics store Healthy Fit. Police charged the owner of the store and two employees in July 2015, alleging that they took more than $4 million from Manulife Financial through false benefits claims.

“Healthy Fit and the employee making the improper or fraudulent claim would then share the money paid out by the TTC’s insurer at the time,” read a statement from the TTC Thursday.

Police have not charged any TTC employees so far, the statement said. However, police are still looking into the scheme, as are TTC investigators conducting an internal inquiry.

In 2016 alone, the TTC saw a $5 million reduction in benefits claims from the year before. A statement from the TTC said that reflected “continued success” in addressing the alleged wrongdoing.

The TTC changed benefits providers on Jan. 1 after a public procurement process, and now uses Green Shield.

Manny Sforza, the temporary head of the TTC workers union, said Thursday he didn't have enough information to comment. Sforza was installed as trustee of Amalgamated Transit Union Local 113 two weeks ago amidst a dispute over union leadership.