More charges against “individuals and entities” are being considered as investigations into allegations of corruption within Fifa have expanded, says US attorney general Loretta Lynch.
In May, 14 Fifa officials and sports marketing executives were indicted in the US on racketeering charges involving more than $150m (£97m).
“Substantial evidence” has been gathered so far, according to Lynch.
Properties in the Alps have been seized in a separate Swiss investigation.
“The scope of our investigation is not limited, and we are following the evidence where it leads,” said Lynch.
“I am grateful for the significant cooperation and substantial evidence that we have received from all quarters.”
In June, Fifa president Sepp Blatter announced he would resign just one week after he was re-elected, saying that “his mandate did not appear to be supported by everyone”.
Lynch would not confirm whether Blatter, 79, is a target of the US investigation.
The Swiss investigation is looking into bids for the 2018 and 2022 World Cups, to be held in Russia and Qatar respectively.
Swiss attorney general Michael Lauber said 11 terabytes of information had been seized “so far” in relation to the investigation, and that it was “not even at half-time”.
Lauber confirmed that Swiss prosecutors will also investigate a Fifa contract for media rights to the 2010 and 2014 World Cups.