A whistleblower has given potentially key evidence to Swiss prosecutors in their investigation of FIFA and suspended president Sepp Blatter.

The spokesman for Switzerland's attorney general's office, Andre Marty, revealed progress in the case in an interview broadcast Thursday by German network ARD.

"A witness, a so-called whistleblower, gave us interesting information relevant to the case, which brought us markedly forward in the criminal investigation," Marty said.

Swiss attorney general Michael Lauber opened criminal proceedings against Blatter four months ago. The next day, Blatter was quizzed at FIFA and his office was raided immediately after chairing an executive committee meeting.

Blatter is suspected of criminal mismanagement and misappropriation of FIFA money linked to a $2 million payment to Michel Platini and selling undervalued World Cup TV rights for the Caribbean to then-FIFA vice president Jack Warner.

Blatter signed a contract in 2005 that gave Warner, a key powerbroker in FIFA elections, control of regional rights the 2010 and 2014 World Cups for a total of $600,000. Warner then sub-licensed the rights to broadcasters for sums reported to be more than $15 million.

Marty said formal charges could be brought by the end of the year.

Blatter faces a jail sentence of up to five years if convicted.

"I think that it will be clear by the end of 2016 to the middle of 2017 whether there will be enough evidence to bring about a prosecution," Marty said.

The intervention by Swiss authorities led the FIFA ethics committee to provisionally suspend Blatter and Platini in October, then ban both for eight years last month. Both deny wrongdoing and have appealed against their sanctions.

Blatter still hopes to host the FIFA presidential election congress on Feb. 26 in Zurich, when his replacement will be elected.