The German sports website RevierSport posted the news on their official twitter page.
Helmer spent six years at Dortmund from 1986-92 and made 190 appearances for the club. The former German international also had spells at Bayern Munich, Sunderland and Hertha Berlin.
Barca Blaugranes recently stated that the Barcelona had stuck a ‘verbal agreement’ with Dortmund for Gündoğan. Barcelona based newspaper Mundo Deportivo claimed that Gündoğan had passed a medical with the Catalan Giants last weekend.
Both Arsenal and Manchester United have been closely linked with the 24-year-old over the past month. The Dortmund star is also reported to have attracted interest from Manchester City according to the Manchester Evening News.
Gündoğan has five assists and three goals in 31 appearances for Dortmund despite spending much of the season out injured and is almost certain to leave the Bundesliga outfit over the summer.