A warehouse fire that sent large plumes of black smoke billowing across Port Phillip Bay has been contained in Melbourne's west.

Fifty firefighters controlled the blaze behind a Spotlight warehouse in Laverton North about 11.15am.

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The Spotlight warehouse on Boundary Road was evacuated but a Melbourne Fire Brigade spokeswoman said only grassland and the pallets were damaged in the fire.

A spokeswoman for the MFB says the fire was started when a discarded cigarette came into contact with combustible material, in this case wooden pallets.

Commander David McCurdy from the Metropolitan Fire Brigade  said grass, wooden pallets and carpet rolls were burning along the north-western side of the Spotlight warehouse. An empty grass field next to the warehouse also caught fire.

"There was large amounts of plastic down the side of the warehouse and the black smoke was coming from the plastic,'' Commander McCurdy said.

He said today's weather conditions were extremely bad for fires, and there were fears the grass fire would spread to surrounding buildings.

"(On a) hot day, (with a) northerly wind and a bit of a small fire operating, it can get into a factory pretty quickly,'' he said.

The fire was under control 50 minutes after it was first reported. The exterior of the Spotlight distribution centre is charred, but there is no internal damage.

General manager of marketing at Spotlight, Jono Gelfand, said packaging lying outside the warehouse was damaged.

"We do know there were some pallets there that were ready to be taken away, and we have got some plastic barriers and it appears that is what caused the thick black smoke that was more dramatic than the fire,'' Mr Gelfand said.

About 90 staff were evacuated from the warehouse, but they returned to work once the fire was under control.