SAO PAULO, Nov 26 (Reuters) - Brazil's Itajai port, which ships meat from the world's top beef exporter, has halted operations after heavy flooding that killed at least 84 people in Santa Catarina state and damaged its two berths, port officials said on Wednesday.

Flood waters in the southern state triggered mudslides that buried homes and swept cars from the road. Around 100,000 people have been cut off from help after the deluge submerged roads. Many have been without food for days and 30 people were missing.

"The floor of one of the warehouses collapsed together with the berth," said an Itajai spokeswoman.

It could take up to six months to complete the repairs needed but the port is expected to be operational again within a week or two subject to safety checks.

Frozen food firm Sadia <SDIA4.SA> said it used Itajai to ship its produce but said the port's closure has not had a significant impact on exports and it was now using the country's largest port, Santos, located in Sao Paulo state.

The world's second largest long-rolled steel producer Gerdau <GGBR4.SA> said it had to reduce output and was seeking alternative fuels to run its plant, being one of around 90 firms affected by the rupture of a gas duct in the town of Gaspar, cutting supplies.

Separately, the port of Paranagua, which ships a large portion of the country's huge grain output, including soy and corn, said it was doing scheduled maintenance at its three berths and would close them one at a time until the works are completed by Jan. 30.

It said that the between-season lull in grains output meant this would have minimal effect on shipping. Maintenance on its silos are also expected to begin in January it said. (Reporting by Eduardo Simoes and Peter Murphy)

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