Selby has a rate of 111.5 cases per 100,000 people following the outbreak, understood to be centred at a warehouse near the town centre.
The outbreak is being managed by Public Health England.
The UK average is 25 cases per 100,000 people and the North Yorkshire average is 28. Cases in Selby have sharply risen from a rate of 48.6 cases last week.
Some 73 people have tested positive for the virus in Selby over the past seven days, according to the data.
The workplace has not been closed but on-site testing support has been made available to staff.
Public Health England also confirmed that tracking of any community spread from the workplace is underway.
Louise Wallace, North Yorkshire’s Director of Public Health said: “The company is working very closely with us as we take every measure, including workforce testing on site, to contain this outbreak.
“As a consequence we know that local infection rates will appear higher and show a short term increase before they start to drop again.
“However, this outbreak only serves to highlight that Covid-19 is still circulating among the population and shows how easily the rate can spike.”
It comes as the UK recorded six further deaths due to coronavirus and 2,064 new cases.
Some 79,695 first and 260,801 second doses of the vaccine were given yesterday
An expert from the University of East Anglia has said the confirmation of the outbreak being linked to a workplace rather than community spread is “reassuring.”
Professor Alastair Grant, who works alongside Public Health England in tracking case rates, said: “It’s very reassuring because it’s not uncommon to see that kind of a spike in a workplace. The concern was that it might be some community outbreak.
“When you have outbreaks on this scale in small districts, it can increase the rate very substantially.”