Garcia "is currently in Zurich and is also interviewing some of the FIFA executive members as part of his ongoing work," FIFA said in a statement Thursday.
Blatter and 12 colleagues, including UEFA president Michel Platini and Russian sports minister Vitaly Mutko, remain on FIFA's board from the December 2010 vote that handed the 2018 World Cup to Russia and the 2022 tournament to Qatar.
The bidding process was tarnished even before the vote by widespread allegations of rule-breaking by bidders and favour-seeking by the FIFA ruling committee. Two voters were suspended by FIFA following a cash-for-votes sting by British newspaper The Sunday Times.
Among nine voters who have since left FIFA, Mohamed bin Hammam of Qatar was banned for life by the governing body in 2012 for financial wrongdoing when leading the Asian Football Confederation.
Garcia's investigating team is focusing on FIFA board members after seeking interviews since last October with officials from the nine World Cup bid committees.
His work resumed this week as further suspicion was cast on bin Hammam's role in the Qatari victory.
The Daily Telegraph in London reported it had evidence of a $2 million money trail from a construction company in Doha controlled by bin Hammam to disgraced former FIFA vice-president Jack Warner of Trinidad and Tobago. One note was dated Dec. 15, 2010.
The newspaper reported that the FBI is investigating links between Warner and bin Hammam, who were FIFA board colleagues for 15 years.
The Qatari World Cup organizing committee has denied persistent allegations of wrongdoing connected to its bid, and distanced itself from bin Hammam, describing him as a "private individual."
Garcia's law firm in New York, Kirkland and Ellis LLP, has said his investigation should extend "at least several months into 2014."
The former U.S. Attorney has had access for more than a year to a whistleblower hotline opened for potential FIFA evidence. He promised anonymity to those providing information.
"As with any investigation, the ethics committee does not comment on ongoing proceedings," Kirkland and Ellis said in a statement Thursday on behalf of the investigations panel.
Garcia will submit a report to the judging chamber of the FIFA Ethics Committee, led by Joachim Eckert of Germany, which will decide possible sanctions.
Blatter has insisted Russia and Qatar will host the World Cup regardless of the investigation's conclusions.
Garcia's firm, said last October that it is not for the ethics committee "to determine the venue or timing of the World Cup."
FIFA is expected to decide early next year whether to switch the 2022 World Cup to November and December from its traditional June-July slot to avoid the searing desert heat in Qatar.
Russia defeated bids from England, Spain-Portugal and Belgium-Netherlands. Qatar beat the United States, Australia, Japan and South Korea.
Garcia is barred by the Russian government from entering the country for his previous work prosecuting an arms dealer who is jailed in the U.S. He has delegated interviews of Russia's bid team — and of American officials — to a Swiss lawyer who is his deputy chairman of FIFA investigations.