Jan Ullrich, the only German ever to win the Tour de France, was held on suspicion of assaulting a prostitute on Friday, as he returned to his native country seeking a fresh start to recover from drug and alcohol problems.
The former star was arrested within hours of arriving back in Germany on Friday. He had announced he was returning to Germany to begin treatment for drug and alcohol problems after his arrest in Spain last week on suspicion of breaking into the villa of a German film star and threatening his guests.
"I have a good gut feeling. This will be a fresh start," Mr Ullrich told Germany's Bild newspaper at his villa in Mallorca shortly before flying back to Germany by private plane. But he was back in a police cell on Friday after being arrested in the early hours of the morning at the five-star Villa Kennedy hotel in Frankfurt.
German police confirmed that a 44-year-old hotel guest had been arrested following a "physical confrontation".
"The guest had quarrelled with a woman escort who was staying with him, in the course of which he is suspected of physically attacking and injuring her," police said in a statement, adding that the alleged victim "had to undergo medical treatment for her injuries".