A foreign worker who was allowed to avoid isolation broke the rules by going straight to work rather than waiting for the result of their first coronavirus test.
The test revealed they were positive.
Jersey's Health Minister has admitted that the worker was one of the 82 from amber or red regions exempt from quarantine.
They were placed into isolation straight away. It is not known if they infected any colleagues.
In the States Assembly Deputy Kirsten Morel asked the Health Minister what restrictions are in place for the foreign nationals who are working on the Horizon development at the Waterfront.
In response Deputy Richard Renouf says the government agreed that some foreign workers would be exempt from isolation rules back in August, and later this was extended out so other companies could apply for similar permissions
Endorsement for permission not to isolate for work purposes was given to the workers on the basis that the permission only applied to the period of time the workers were at work and subject to adherence to the risk management plans submitted by the company involved.
In a written response Deputy Renouf said workers are only exempt from isolation for the time they are at work. He said they must take an initial test upon arrival and isolate until that test result comes back negative.
He added the decision to grant these permissions were made on this basis of advice given by Dr Ivan Muscat.
Since mid September 82 workers have been allowed to work in Jersey without having to self-isolate on arrival.
These included engineers working at Bellozane, Ports of Jersey staff and those responsible for inspecting specialist or heavy machinery which must be inspected by law.
The permissions only apply to the time the worker is at or travelling to and from work. Outside of this, they must isolate in accordance with the restrictions relating to their travel history.
Those who are exempt are monitored by the island's Monitoring and Enforcement Team.