"If evidence should emerge that the awards to Qatar and Russia only came about thanks to bought votes, the awards could be invalidated," Domenico Scala, the independent chairman of FIFA's audit and compliance committee, said in an interview with SonntagsZeitung.
"This evidence has not yet been brought forth," he added.
Swiss prosecutors earlier opened a case to probe into alleged violations during the bidding process.
Russian officials claim that there is no threat to hosting the 2018 World Cup in Russia.
"We've got a contract signed, the FIFA Executive Committee took the decision in 2010, the congress supported this decision. [Independent ethics investigator Michael] Garcia's report has revealed that there are no corruption-related claims against Russia," Russian Sports Minister Vitaliy Mutko said.
