Washington (CNN) The Internal Revenue Service believes that a major cyber breach that allowed criminals to steal the tax returns of more than 100,000 people originated in Russia, Rep. Peter Roskam confirmed to CNN on Thursday.

The Illinois Republican, who is chairman of a House subcommittee with IRS oversight, said IRS Commissioner John Koskinen told him about the theft's Russian provenance in a phone call.

CNN first reported the breach's Russian origin on Wednesday.

"It's a problem, no matter where it's coming from, for the taxpayers and the IRS. It surely doesn't help matters though that it's coming from Russia for all the obvious geopolitical reasons," Roskam said.

The IRS announced Tuesday that organized crime syndicates used personal data obtained elsewhere to access tax information, which they then used to file $50 million in fraudulent tax refunds.

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