Firefighters have been battling a huge factory fire at a food processing plant in Gembrook.

The blaze at the Mountain Harvest Food factory in Mountain Road started in the early hours of Wednesday morning.

Commander Paul Carrigg said crews were called at 1:30 AM following a number of calls.

He told the Herald Sun “Our crews could see flames on the way there, it was well alight, the factory was totally involved by fire. We were hampered by limited water supplies and heavy rain but we managed to save 50 per cent of the plant.’’

The blaze took 60 firefighters more than 3 hours to bring under control.

Smoke will be visible in the  Cockatoo, Gembrook, Mount Burnett areas this morning.

It is not known what caused the fire.