Australian Police are searching the wreckage of a helicopter which crashed at Mount Disappointment, north of Melbourne, with five people on board, ABC reported.

Victoria Police said two helicopters were travelling north in a convoy from Melbourne's CBD over Mount Disappointment when one disappeared just after 9:30am.

Police spotted the missing helicopter from the air about 11:45am, and are preparing to begin a ground search of the area.

A pilot and four passengers were on board, and it is not yet known what went wrong or if anyone survived.

The ABC understands the helicopters were operated by a private charter company.

Ambulance Victoria crews were called to the scene about 9:35am and the State Emergency Service is also responding.