The scrub fire started in bushland near Paddington Avenue in Carrum Downs about 3pm and tore through about four hectares before it was brought under control before 6pm.

Residents whose gardens backed onto the area had to use garden hoses to keep the flames at bay and a section of Peninsula Link was closed to traffic while emergency crews battled the fire.

The CCTV shows a man moving about a grassed area near Paddington Avenue around the time of the fire. Police believe he may be able to assist them.

Police have been treating the fire as suspicious since Wednesday night.

"There's no other reason how the fire should have started," Detective Sergeant Gary Edwards told Channel Nine on Wednesday.

The fire comes less than week after police launched 'Operation Firesetter' to crack down on firebugs who deliberately light grass fires over the holiday period.

The operation focuses on arson detection and prevention in at-risk areas and monitors potential fire-starters.

More criminal offences for causing bushfires have been recorded in Victoria over the past five years, driven by arsonists who light multiple fires.

Crime Statistics data shows there have been four "cause a bushfire" offences in Carrum Downs over the past five years: 

Police are urging anyone with information on the Carrum Downs fire to contact Crime Stoppers on 1800 333 000.