The FBI is said to be investigating yet another suspected hack of a Democratic Party organization, this time of the Democratic Congressional Campaign Committee that raises funds for Democrats running for the House of Representatives.

The previously unreported hack of the DCCC is likely to have been aimed at gathering information on donors rather than steal funds, four sources told Reuters.

The intrusion is likely to raise fresh concerns about Russia trying to meddle in the U.S. elections. Another hack of the Democratic National Committee, suspected by security investigators to have been perpetrated by Russians, led to an embarrassing dump on Friday of leaked emails that showed that the Democratic Party's national strategy and fund-raising committee had favored Hillary Clinton over Senator Bernie Sanders, her rival in the presidential nomination campaign.

The release of the emails by whistle-blowing website WikiLeaks, which did not disclose its source, led to the resignation of DNC Chairwoman Debbie Wasserman Schultz. The FBI said earlier this week it was investigating the attack on the DNC. “A compromise of this nature is something we take very seriously," it said.

The DCCC hack could have begun as recently as June and involved the setting up of a “spoof website” with a name similar to that of the main donation site of the organization. That tricked campaign donors for some time to visit the spurious site rather than the company that processes the donations, according to the Reuters news report on Thursday.

A possible tell-tale sign of Russian intervention again is that the IP address of the spurious site was similar to one used by a hacking group linked to the Russian government, according to the report. This group is one of two such groups suspected in the DNC hack.

The DNC is having a convention this week at Philadelphia at which Clinton is expected to accept on Thursday her nomination as candidate for president. The FBI could not be immediately reached for comment.