Police are investigating whether a manager at a major bus company was for five years secretly selling spare bus parts for a profit.

A workshop manager at the Keysborough and Heatherton depots of Transdev was sacked on Thursday last week, after the international corporation detected potential theft and referred the man to police.

Transdev has referred the matter to police. Credit:Daniel Pockett

Under the scheme, the manager allegedly ordered surplus spare bus parts for the company and privately sold them on, pocketing the cash.

Police are investigating incidents that allegedly took place at locations across Melbourne between 2013 and 2018.