Rep. Elijah E. Cummings of Maryland sent a letter telling the head of Strategic Allied Consulting to make himself available for an interview by Oct. 12, the Los Angeles Times reported Tuesday.
In addition, Cummings asked Nathan Sproul to provide copies of his correspondence with the Republican National Committee and state political parties.
Cummings is the ranking Democrat on the House Oversight and Government Reform Committee.
Last week, the RNC severed ties with Strategic Allied Consulting after election officials in Florida's Palm Beach County discovered potentially fraudulent voter registration forms submitted by one of its workers.
Since then, 10 other Florida counties have reported suspicious voter registration applications linked to the firm.
Isolated reports of registration irregularities are being investigated in Colorado, Nevada and North Carolina.
The GOP directed at least $3.1 million to the firm through state parties.