Washington (CNN) Justice Department special counsel Robert Mueller is comparing notes with the office of New York Attorney General Eric Schneiderman on the Russia investigation, a source familiar with the investigation told CNN Thursday.

The two offices' discussions include the New York attorney general's investigation into former Donald Trump campaign chairman Paul Manafort, which started earlier this summer, the source said.

Politico, citing several people familiar with the matter, first reported on Wednesday that Mueller had teamed up with Schneiderman to investigate Manafort and his financial transactions.

It's not unusual that both offices would be talking to one another about the probe, the source familiar told CNN, since they are working on the same investigation. The source added that some of the investigators working in Mueller's office come from the Southern District of New York, adding to the closeness between the two offices.

A spokesman for the office of special counsel declined to comment.

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