The Federal Election Commission is investigating Ilhan Omar.
The FEC has asked for more detail about thousands of Omar's donors, who gave less than $200 each.
These contributors poured more than $800,000 into her re-election bid over a three-month period.
Agency staff sent a letter to the Minneapolis Democrat’s campaign in late November.
The FEC wants more information about the large share of cash from individuals giving $200 or less.
$200 or less is the maximum allowed before triggering donor disclosure requirement.
These contributions accounted for more than 75% of the $1.1 million Omar reported raising from July to September.