NHS Tayside has confirmed the number of cases connected to the coronavirus cluster at Coupar Angus has risen to 90.
79 factory workers at the 2 Sisters food processing plant have tested positive for the virus and the remaining 11 cases are from community contacts.
Health board bosses say detailed contact tracing is taking place and hundreds of workers have had tests over the last few days.
Factory workers who have yet to get tested are being urged to do so even if they have no symptoms.
Dr Emma Fletcher, Associate Director of Public Health for NHS Tayside, said: “The figures for Tayside as a whole rose significantly in the last 24 hours and our initial review of this total has identified that the overwhelming majority of these new cases look to be linked to the 2 Sisters factory.
“We are undertaking detailed contact tracing of these positive cases to ensure everyone fully understands what action they must now take.
“Hundreds of workers from the factory have attended for testing over the past couple of days and therefore we absolutely expected to see the number of positive cases linked to this outbreak increase. Given the volume of testing which has now been completed, we expect this number to rise further in the coming days as tests are processed and we receive the results.
“We remain in a heightened state of vigilance right across Tayside and I would stress again the fact that all workers and their household contacts, including children, should self-isolate until 31 August. Even if they have a negative result they must continue to stay at home and not leave their house until 31 August.
“People may be feeling a little more anxious given the increase in positive cases in Tayside. Our advice remains for everyone across the area to be extra vigilant in following the FACTS guidance, particularly the over 70s and those who were shielding or in high-risk groups.
“Additional testing units have been made available over the weekend and into next week and we would urge all those factory workers who have not been tested to attend, even if they do not have any symptoms.”
Dedicated mobile testing units for 2 Sisters factory workers will be onsite at the factory as well as at Blackness Fire Station on Sunday August 23 between 10am and 6pm.
There are also mobile testing units at Broxden Park and Ride in Perth until Monday August 31, from 10am to 6pm as well as Forfar Fire Station also from 10am to 6pm.
The regional testing centre remains at Dudhope Castle and is open from 8am to 8pm.