Hundreds of staff were tested at the food factory in Pool, a village near Redruth.
Most of the positive cases at the Pilgrim's Pride meat plant were asymptomatic, according to the local public health team.
The company says it has introduced additional measures and checks its compliance with Covid-19 controls on a daily basis.
An alert to the national test and trace service from a single member of staff led to 500 colleagues at the plant being tested.
A spokesperson for Pilgrim's Pride added: "From the outset we have worked conscientiously to do all we can to protect our workforce and the local community.
"Our teams have been working extremely hard in collaboration with the local authority and public health to manage this challenging situation, and have bravely conducted themselves with professionalism and integrity as they continue to play their important role in maintaining the UK food supply chain."
Rachel Wigglesworth, interim director for public health for Cornwall Council, said her team had strengthened the “local Covid-19 contact tracing approach to help detect cases early, prevent spread and support people to self-isolate”.
“We've quickly identified and tested hundreds of people, and in finding people who weren't displaying symptoms we have potentially stopped much wider spread in our communities,” she said.
“We continue to closely monitor the situation and appreciate the cooperation of Pilgrim's Pride Ltd. and their employees.”
It is not the first time coronavirus clusters have been reported at food factories in the UK.
A chicken plant in Wales temporarily shut in June after more than 150 employees tested positive.
Around the same time, a meat-packing plant in West Yorkshire dealt with a Covid-19 outbreak.
Additional reporting by Press Association