WASHINGTON — (CNN) Hackers connected to the Russian government broke into the servers of the Democratic National Committee and stole opposition research on Donald Trump, according to the cybersecurity experts who responded to the intrusion.

Two separate Russian intelligence-linked cyberattack groups were both in the DNC’s networks, said Dmitri Alperovitch, co-founder and chief technology officer of CrowdStrike, on Tuesday, which responded to the breach.

They likely didn’t even know the other was in the systems, he added.

The breach was first reported by The Washington Post.

CrowdStrike was enlisted by the DNC early last month after the DNC suspected something was amiss in its servers.

The hackers were kicked out over the weekend, Alperovitch said, and CrowdStrike is monitoring for any efforts by them to hack back in.

“The security of our system is critical to our operation and to the confidence of the campaigns and state parties we work with,” DNC Chairwoman Rep. Debbie Wasserman Schultz said in a statement.

“When we discovered the intrusion, we treated this like the serious incident it is and reached out to CrowdStrike immediately. Our team moved as quickly as possible to kick out the intruders and secure our network.”

The group that stole Trump’s opposition file got in a few months ago and is linked closely with a Russian military intelligence organization, Alperovitch said.

A different Russian group was monitoring the communications servers of the DNC, including email, for about a year.

“I have high level confidence that this is Russian intelligence,” Alperovitch said, citing a vast body of research his company has on the unique indicators of various cyberattack groups around the world. CrowdStrike specializes in groups known as “advanced persistent threats,” or high-level, often government-linked hacking entities.

A Department of Homeland Security official told CNN the agency is aware of the reports and is currently looking into the matter.