Three bodies have been retrieved and a fourth person is believed dead after a small plane plunged into the ocean off Barwon Heads near Geelong.

The light passenger plane from Moorabbin Airport crashed into the ocean off the Victorian coast about 12:30 p.m. this afternoon.

Police say the crash, two kilometres off Collendina Beach between Barwon Heads and Point Lonsdale, was called in by a fisherman.

The three bodies were found amongst the wreckage.

The crash site is at least 2.5km from the coast, off the Buckley Park Foreshore Reserve.

The coast guard is sifting through floating fragments of the plane.

Don Adamson from the Barwon Heads Airport told AAP that all planes from that airport had been accounted for and they didn't know where it had flown from.

Police and emergency services were on scene with two air ambulances.

The cause of the incident is not yet known.

Australian Transport Safety Bureau says it is investigating but has no details yet.

Police will have a press conference outside Queenscliff Coast Guard Office at 3:30 p.m. AEDT.

Scene of crash appears to be on flight route used by light aircraft (like this Piper) headed for Tasmania. pic.twitter.com/aIbDJzbQqE

- Samuel Clark (@sclark_melbs) January 29, 2016