German football chiefs are not ruling out the involvement of players in the country's match-fixing scandal.
"It's not something you can exclude," German Football Association (DFB) co-president Theo Zwanziger told the Stuttgarter Nachrichten newspaper when asked if players could have been involved.
"That's something that causes me great pain."
Berlin-based referee Robert Hoyzer has admitted DFB allegations that he rigged matches after betting on them are essentially true.
Hoyzer has told prosecutors in Berlin that other referees and some players were involved in match fixing, the Sueddeutsche Zeitung, a leading German daily newspaper, reported on Friday in a preview of its Saturday edition.
Hoyzer told authorities he was present when referees received payments and had heard about payments to players, the paper reported, without naming the source of its information.
He also admitted receiving 50,000 euros ($65,190) for fixing three matches, the paper said.
Investigations are concentrating on a first round Cup tie, two second division games and three others from the regional league but the country's Bundesliga chief warnedthat the scandal could yet draw in matches played at the highest level.
"I don't want to exclude the possibility of an attempt being made there (in the first division)," Bundesliga president Werner Hackmann said in an interview with Hamburg 1 television.
"Naturally, it's more difficult to achieve something like that when you have a refereeing observer and TV cameras there."
The 25-year-old Hoyzer said already on Thursday that more people in football were involved and said that he had profited by a five-figure sum.
The Sueddeutsche Zeitung reported on Friday he told prosecutors the other referees and players involved had fixed matches in the second division.
Public prosecutors are investigating alleged links with Croatian gamblers. Two arrests were made on Friday during police searches of four locations in Berlin, according to the city prosecutor.
Separately on Friday, the president of Munich-based bookmaker Oddset, Erwin Horak, said at a news conference the company planned to take Hoyzer to court after it lost around one million euros on two allegedly fixed matches.
(additional reporting by Iain Rogers)