Amazon.com Inc. says it’s aware of almost 20,000 employees who have tested positive for Covid-19 during the pandemic, a disclosure that follows criticism from some lawmakers and employees that the world’s largest online retailer was insufficiently transparent about outbreaks within its ranks.

The retailer said in a blog post today that 19,816 employees tested positive for the respiratory disease, or were presumed positive, out of 1,372,000 people who worked for the company from March 1 to Sept. 19. The company says that if its employees contracted the virus at a rate equal to that of the general population, Amazon would have seen some 33,952 cases.

Amazon has dealt with outbreaks of Covid-19 at facilities in Europe and the U.S. Company data published alongside the blog post on Thursday show that Amazon’s case rate was lower the expected rate for an employer of its size in most U.S. states where the company operates.

One exception is Minnesota, where an Amazon warehouse outside Minneapolis dealt with an outbreak among employees in which the infection rate exceeded the prevailing rate in the community, Bloomberg reported in June.