Dortmund had been due to hold a public training session to showcase its squad, bolstered by the signings of Donyell Malen and Gregor Kobel, though they had to postpone due to positive tests among the first-team group.
Following the positive COVID-19 test of Thomas Meunier, there has unfortunately been another positive case from testing following the player's day off.— Borussia Dortmund (@BlackYellow) August 3, 2021
Julian Brandt has tested positive for COVID-19 and we wish him a symptom-free and speedy recovery 🙏 pic.twitter.com/cpEUibfsIR
The club initially announced Meunier's COVID-19 results with a statement, before releasing details of Brandt's test on Twitter as they communicated the cancellation of the open training session.
The statement concerning Meunier on the official website said: "Borussia Dortmund defender Thomas Meunier has tested positive for coronavirus. The Belgium international took two tests prior to the training camp in Switzerland and an additional test before departing from Bad Ragaz. All of those tests came back negative.
"Having had several days off, the player has now tested positive before commencing training this week. Thomas Meunier has since been in isolation. We hope that Thomas' symptoms are as mild as possible and that he gets well soon."
Later on Tuesday, Dortmund's official Twitter account posted the news that Brandt, too, had tested positive.
Marco Rose's new side finished third in Bundesliga last term, with a late push securing Champions League football for the 2021-2022 campaign.
The German side failed to keep hold of Jadon Sancho, who moved to Manchester United in the transfer window, though they do still have Erling Haaland to call upon for the new season.
Dortmund gets its Bundesliga campaign underway against Eintracht Frankfurt on 15 August before facing Bayern Munich in the DFL-Supercup three days later.