The new betting scandal that broke late last week, widened on Monday, with two clubs admitting that their players had been approached to throw matches.
Third division clubs Eintracht Trier and SpVgg Bayreuth said that an unnamed player from their team had been approached to fix matches, but both players had turned down the request and reported it to their clubs.
Frankfurt prosecutor Thomas Bechtel, who is in charge of the investigations, told Deutsche Presse-Agentur, dpa he did not want to comment on "names and clubs," but added that he could not rule out the scandal widening further.
The four suspects who were arrested on the weekend and who have not yet applied for bail, are to be interviewed by justice officials in the next few days.
Investigators are also hoping that they will be able to ascertain the extent of the match fixing attempt after analysing evidence - such as computers - they secured from the suspects.
"If we find out that others are involved, we will extend our inquiries," Bechtel said.
The Frankenpost newspaper reported Monday that the apartment of the Bayreuth player, who had telephonic contact to one of the suspects, was searched. His club said however, that no incriminating evidence was found and that no further investigations were planned.