The U.S. Internal Revenue Service believes the theft of about 100,000 taxpayers' personal data from its computer system originated in Russia, CNN reported on Wednesday.
The tax agency's criminal unit is leading an investigation into the cyber attack, in which criminals stole information through an online IRS application over the course of four months, and the Treasury Department's inspector general and the Department of Homeland Security are also looking into the breach, CNN said.
The IRS would not comment on the hackers' identities during a news conference on Tuesday when it informed the public of the thefts.
IRS hack traced to Russia
US IRS tax data hack traced to Russia: CNN
This April 13, 2014 photo shows The Internal Revenue Service Headquarters (IRS) building Washington. The Internal Revenue Service already has received nearly 100 million tax returns, but anticipates getting about 35 million more by the midnight Tuesday deadline. Many other taxpayers, however, are opting for plan B and asking for more time to file. (AP Photo/J. David Ake)
Internal Revenue Service (IRS) Commissioner John Koskinen arrives on Capitol Hill in Washington, Wednesday, April 15, 2015, to testify before the Senate Homeland Security and Governmental Affairs Committee hearing to examine IRS challenges in implementing the Affordable Care Act. (AP Photo/Andrew Harnik)
A view of an IRS 1040 Tax Form on a Laptop computer screen being prepared for an electronic filing.
The Internal Revenue Service building at the Federal Triangle complex in Washington, Saturday, March 2, 2013. (AP Photo/Manuel Balce Ceneta)
WASHINGTON, DC - JULY 22: The Internal Revenue Service Building is shown July 22, 2013 in Washington, DC. Due to current shortfalls in the federal budget, all Internal Revenue Service operations are closed today, with another furlough day scheduled for next month. (Photo by Win McNamee/Getty Images)
Discover More Like This
BACK TO SLIDE
On Wednesday, the IRS had no immediate comment to the CNN report.
Meanwhile, the Senate Finance Committee, which oversees the IRS, said that it will hold a hearing on Tuesday on the data theft.
IRS Commissioner John Koskinen is scheduled to testify, the committee said, along with J. Russell George, the Treasury Department's inspector general for tax administration.