There are now 37 COVID-19 cases linked to Imperial Oil’s Kearl Lake site north of Fort McMurray.
A company spokesperson says 10 individuals are in quarantine on-site.
The other 27 who are self-isolating off-site started developing symptoms while they were away from the oilsands.
Each of the individuals were also tested off-site.
Imperial only started testing employees on-site earlier this week with help from Alberta Health Services.
It isn’t mandatory, however, the company is recommending everyone get swabbed because people with the virus can be asymptomatic.
Dr. Deena Hinshaw, Alberta’s Chief Medical Officer of Health, announced on Wednesday that seven of the individuals were in other provinces. Five in British Columbia, one in Saskatchewan, and one in Nova Scotia.