The U.S. believes that people working for the Russian government are behind the hack of internal emails at the Democratic National Committee, officials confirmed Tuesday to CBS News.

A U.S. intelligence official told CBS News that the signature of the breach is Russian and the U.S. government has identified methods and techniques used by Russia in past hacks that mirror those used in the DNC incursion.

“We understand how hack groups use the Internet to attack. The pattern and launch point used before by Russians is similar to the DNC attack,” the official said.

A cyber analyst quoted by the Associated Press, Michael Buratowski with Fidelis Cybersecurity, which investigated the hack, said he was near certain that Russia was the culprit, based on the use by the hackers of “Russian internet addresses, Russian language keyboards, and the time codes corresponding to business hours in Russia, as well as the sophistication of the hack,” according to the AP.

The official also said the “DNC was told before the convention that something was going on,” but “they took some time to respond.”