Philadelphia - The FBI is investigating an apparent hack into computer systems at the Democratic Congressional Campaign Committee, following a similar intrusion at the Democratic National Committee.A Democratic aide says House Democratic leadership has been informed of the investigation. The aide demanded anonymity to discuss an ongoing investigation.Details weren't immediately clear. The Democratic Congressional Campaign Committee is the campaign arm for House Democrats.Cybersecurity experts who studied the hack at the DNC have blamed Russia. That hack exposed embarrassing emails indicating supposedly neutral DNC officials maneuvered in favour of Hillary Clinton over Bernie Sanders. That resulted in party chairperson Rep. Debbie Wasserman Schultz announcing her resignation just as the Democratic National Convention was getting under way in Philadelphia.The DCCC hack investigation was first reported by Reuters.