The FBI's investigation of bribery and corruption at FIFA includes scrutiny of how soccer's governing body awarded World Cup hosting rights to Russia and Qatar, a U.S. law enforcement official told Reuters this week.
"If evidence should emerge that the awards to Qatar and Russia only came about thanks to bought votes, then the awards could be invalidated," Scala told SonntagsZeitung in an interview published on Sunday.
"This evidence has not yet been brought forth."
Russia and Qatar have denied wrongdoing in the conduct of their bids for the 2018 and 2022 tournaments, which were not the subject of charges announced by U.S. prosecutors last week against FIFA officials.
Scala made similar comments in 2013 but events over the last two weeks, which included a dawn police raid in Zurich and the arrests of several FIFA officials on U.S. charges, have added urgency to his remarks.
British Foreign Secretary Philip Hammond said he supported Qatar hosting the 2022 tournament but said Britain would work with another country if FIFA re-opened the bidding process.
"We would offer our support to any country that has been chosen to host the World Cup," Hammond told BBC World Service radio, saying the final decision would be for FIFA to make. He ruled out any British bid to host the 2022 competition if Qatar was stripped of hosting rights.
Sepp Blatter unexpectedly announced on Tuesday he was resigning, just four days after securing a fifth term as FIFA president and shortly before it emerged that he too was under investigation by U.S. law enforcement.
In a separate interview with Swiss paper Sonntags Blick, Scala floated the idea of term limits for the FIFA presidency.
"If a FIFA president does two or three cycles that is enough," Scala was quoted as saying.
A representative for Scala confirmed his remarks.
FIFA did not immediately respond to a request for comment.