S.

Treasury Department, as well as an agency that decides Internet and telecommunications policy.

That's according to multiple people familiar with the matter, who also said there is concern within the U.

S intelligence community that the hackers used a similar tool to break into other government agencies.

Three of the people familiar with the investigation said Russia is currently believed to be behind the attack.

Two of the people said that the breaches are connected to a broad campaign that also involved the recently disclosed Hack on Fire I A major U.

S.

Cyber security company with government and commercial contracts.

A National Security Council spokesman said.

Quote the U.

S government is aware of these reports and we are taking all necessary steps, toe, identify and remedy any possible issues related to this situation.

One of the people familiar with the matter said the hack is so serious it lead to a National Security Council meeting at the White House on Saturday.

Sources told Reuters that hackers broke into the National Telecommunications and Information Administration's Microsoft Office 3 65 software and that staff emails at the agency were monitored by hackers for months.

The investigation into the breach is still in its early stages and involves a range of federal agencies, including the FBI, according to three people familiar with the matter.

There is some indication that the email compromise at NT I A dates back to this summer, although it was only recently discovered, according to a senior U.

S official.