An inquiry into allegations that Germany bought votes to win hosting rights for the 2006 World Cup said Friday it could not rule out the possibility that bribes were paid.

“We have no proof that votes were bought, but we cannot rule this out,” lawyers from Freshfields, commissioned by the German Football Federation to probe corruption allegations, said in a report.

Key witnesses “hampered” FIFA’s inquiry into Germany’s bid to host the 2006 World Cup by refusing to give evidence, football’s world governing body added.

FIFA said it welcomed a German inquiry into the German campaign which said it could not rule out that FIFA votes were bought.

“However, many questions still remain to be answered. FIFA’s investigation has been hampered by the fact that key witnesses were not willing to answer questions or provide documents,” said a FIFA statement, which did not give names.

FIFA said it was still cooperating with German and Swiss authorities in their investigations into various World Cup bids.