The Bundesliga side suspended the 20-year-old for missing training after they rejected an offer from Barcelona and Dortmund boss Peter Bosz had admitted he was unaware of Dembele's whereabouts on Thursday before the club later confirmed he remained in the German city.
He said: 'Our focus now is on preparation for the Bundesliga opening match in Wolfsburg.
Dortmund added that they "will not make any more comments on the situation beyond this statement".
His unauthorised absence came after Barca had a bid rejected for the France global, who has been earmarked by the Liga powerhouse to replace Neymar following the Brazil star's world-record €222million transfer to Paris Saint-Germain this month.
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Dortmund kick off their Bundesliga season on Saturday against Wolfsburg and Dortmund director of football Michael Zorc confirmed Dembele would continue to train alone.
Dembele is under contract with Dortmund until 2021 and an initial offer from the Spanish giants has been rejected by Dortmund.
Dortmund have now announced Dembele will be punished for his no-show and will be banned until after this Saturday's DFB-Pokal clash with Rielasingen-Arlen.
'Dembele, of course, has the opportunity to complete an individual training session outside the group'.
Dembele joined Dortmund a little over 12 months ago from Rennes on a five-year contract and scored 10 times in 49 appearances in all competitions last season.