A prison guard at Ravenhall Correctional Centre is being investigated over allegations he withheld food from a vulnerable Aboriginal prisoner.

The guard at the medium-security prison in Melbourne's west was accused of refusing to give the prisoner food for several hours during a recent shift, Corrections sources said.

Ravenhall Correctional Centre in Melbourne's west. Credit:Joe Armao

The Age has been told the inmate raised the fact he was yet to be fed after being moved from his unit to one of the observation cells, which are commonly used to house at-risk prisoners.

He allegedly went a further two hours before complaining again and eventually receiving a meal.