SAO PAULO (REUTERS) - A fire on Friday destroyed up to 300,000 tonnes of sugar and much of the Santos Port warehouses owned by Copersucar, the world's largest trader of the sweetener, the port authority of Santos said.

Copersucar says nearly a fifth of the world's sea-borne sugar trade flows through its trading desks.

ICE March raw sugar prices rose more than 6 per cent to a one-year high on news of the fire, before paring gains. By 8:40am the contract was up 3 per cent at 19.58 cents per lb.

"Three warehouses were destroyed by the fire and we are trying to control the fire now in a fourth," said a representative for the fire department in Santos, adding that four people were hurt.

Copersucar has six warehouses with capacity to hold 50,000 to 100,000 tonnes each at the Santos port, the world's main source of raw sugar shipments. Copersucar officials said they had no additional information about the containment and damage of the blaze beyond what the fire department has reported.

Live television footage showed a three-storey high mountain of sugar engulfed in flames inside a warehouse that had lost most of its siding and roof to the flames.

Some of the overhanging conveyor belts that transport sugar between the warehouses and eventually to waiting ships at the terminal in Santos appeared to have toppled over or were lying on the pavement alongside some of the warehouse.

Brazil is at the tail end of a record 585 million tonne center-south cane harvest that is expected to produce 34 million tonnes of sugar. Roughly 15 per cent of the crop remains to be crushed.

In June, Copersucar had inaugurated an expansion project at Santos that doubled its export capacity to 10 million tonnes a year.

Copersucar represents 47 sugar mills in Brazil and recorded revenues of US$4.1 billion in 2012. The company had hoped in June to expand its trading volume to 9 million tonnes from 7.2 million tonnes in 2012.