Cops called as prisoner climbs onto roof

"The situation remains very dynamic," police said in a statement.

The operation began at the medium-security prison west of Melbourne after police were called at 10am on Wednesday.

Corrections Victoria's security and emergency services unit has also been deployed to support the police response.

"Ravenhall Correctional Centre is currently responding to an incident," a Department of Justice and Community Safety spokesperson said.

The jail houses sentenced and remand male prisoners.

The media has been told not to go to the facility to avoid escalating the situation.

It comes after a separate incident involving another prisoner in September.

A prison officer was hospitalised after allegedly being stabbed by an inmate.