Piling rig falls on Melbourne hospital

A piling rig has fallen onto the roof of a Melbourne hospital, prompting the evacuation of around 70 people from the building.

Emergency service crews were called to Frankston Hospital about 10am on Wednesday to reports of a crane falling on the roof of the building.

The machine has since been identified as a piling rig, used in foundation engineering.

Fire Rescue Victoria crews arrived within five minutes and assisted with the evacuation of patients and staff from the mental health ward.

Victoria Police, Ambulance Victoria and WorkSafe were also called to the scene.

The Department of Health said there were no reported injuries and all patients, staff and site workers were safely evacuated.

The 46 patients have been moved to other wards or different hospitals as investigations into how the rig fell get underway.

Officers have been told the machine was being operated in a construction zone on Yuille Street when it tipped onto the building.

The fallen rig triggered the hospital's fire alarms and sprinkler systems leading to "chaos" for a few minutes, assistant chief fire officer Greg Christison said.

It could take another eight hours to clear the rig from the hospital's roof, he added.

Peninsular Health chief executive Felicity Topp said the Frankston Hospital emergency department and other services would remain open to the public.

"When we know what's happening with the building, we will then determine how we manage our mental health services," Ms Topp told reporters on Wednesday.

Frankston Hospital is undergoing a $1.1 billion redevelopment, including a 12-storey clinical services tower, 130 more beds and new spaces for mental health, oncology and expanded women's and children's services.

Construction is expected to be completed in 2025.