WASHINGTON (Reuters) – The U.S. Democratic Congressional Campaign Committee confirmed on Friday that it had been the target of a cyber security incident similar to other recent attacks, including the theft of documents from the Democratic National Committee.

The DCCC said in a statement that it took immediate action and engaged forensic investigator CrowdStrike to investigate the breach of its systems. The probe is ongoing, it added.

“The DCCC takes this matter very seriously. With the assistance of leading experts we have taken and are continuing to take steps to enhance the security of our network in the face of these recent events,” the committee said in the statement.

“We are cooperating with the federal law enforcement with respect to their ongoing investigation,” it said.

Reuters reported on Thursday that the FBI was investigating a cyber attack against the DCCC that may be related to an earlier hack against the Democratic National Committee.

The potential link to Russian hackers is likely to heighten accusations, so far unproven, that Moscow is trying to meddle in the U.S. presidential election campaign to help Republican nominee Donald Trump.

The Kremlin denied involvement in the DCCC cyber attack.

Hacking of the DNC’s emails caused discord among Democrats at the party’s convention in Philadelphia to nominate Hillary Clinton as its presidential candidate.

(Reporting by Dustin Volz; Writing by David Alexander; Editing by Susan Heavey and Frances Kerry)