The National Republican Congressional Committee said Tuesday it suffered a major hacking attack during the 2018 election.

“The NRCC can confirm that it was the victim of a cyber intrusion by an unknown entity,” NRCC spokesman Ian Prior told Fox News. “The cybersecurity of the committee’s data is paramount, and upon learning of the intrusion, the NRCC immediately launched an internal investigation and notified the FBI, which is now investigating the matter.”

Prior added: “To protect the integrity of that investigation, the NRCC will offer no further comment on the incident.”

The NRCC is the committee dedicated to electing House Republicans across the country. The GOP ended up losing 40 seats in November's elections, as well as its majority.

Politico first reported that the NRCC suffered the cyber intrusion during the midterms.

The outlet cited sources in saying the emails of four senior aides were surveilled for months. Politico reported that GOP officials believe the attack was from a foreign agent.

Politico reported that the Republican leadership, including House Speaker Paul Ryan, House Majority Leader Kevin McCarthy and Majority Whip Steve Scalise had not been informed of the attack until the outlet began reporting its story.

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According to the outlet, the hacking was first discovered by a managed security services provider that monitors the committee’s network.

It comes after the high-profile hack of Democratic campaign committees and other prominent Democrats aligned with Hillary Clinton during the 2016 presidential election. Unlike in those instances, Republicans told Politico they don’t believe any of the information hacked from GOP emails was made public.

Prior to the elections, Trump expressed concern over the possibility of Russia interfering in this midterm cycle. Special Counsel Robert Mueller is prosecuting Russian operatives for targeting the Clinton campaign and Democratic Party during the 2016 election in an effort to help Trump.

“I’m very concerned that Russia will be fighting very hard to have an impact on the upcoming Election,” Trump tweeted in July.

Fox News' Peter Doocy contributed to this report.