The U.S. attorney for the Southern District of New York in Manhattan has opened an investigation into possible money laundering by former Trump campaign chairman Paul Manafort , a source with direct knowledge of the situation has confirmed to ABC News.A spokesperson for Manafort declined to comment to ABC News on Tuesday night.Manafort is already under investigation by special counsel Robert Mueller as part of the probe into possible collusion between the Trump campaign and the Russian government.Additionally, Manafort has been under investigation for possible criminality in New York State by Attorney General Eric Schneiderman . Both the Attorney General and Southern District New York offices are cooperating with the Mueller investigation.The source who confirmed that the U.S. attorney for the Southern District of New York has opened an investigation -- which was first reported by The Wall Street Journal -- points out that it is not uncommon for multiple investigations to be open by different levels of government.