A Chinese fishing company has launched the first phase of investment into a multi-million dollar tuna processing plant in the Marshall Islands.

The Marianas Variety reports the Shanghai Deep Sea Fisheries Company has invested $US8.5 million in a plant in the capital, Majuro.

The existing factory facilities are being torn down so the plant can be doubled in size.

The company says the plant will open in August with about 200 local workers, to be increased each month until full operation by December.

It has promised the Government there will be no less than 90 per cent Marshallese workers, which would be around 600 to 650 local jobs