The story was first reported by Politico, which said the GOP believed a foreign entity was responsible.
The NRCC said it notified the FBI, and launched an internal investigation.
"To protect the integrity of that investigation, the NRCC will offer no further comment on the incident," the statement read.
The story line drew immediate parallels to hacks during the 2016 campaign against Democrats - except the emails and information reportedly accessed does not seem to have been made public.
"This NRCC hack shows cyber security is not a partisan issue," said Rep. Ted Lieu (D-CA).
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