Russian government hackers penetrated the Democratic National Committee’s database and stole its opposition research on Donald Trump, it was reported Tuesday.

DNC officials and security experts say the hackers were able to read all e-mail and chats in the compromised system, according to The Washington Post.

Some of the hackers had been in the DNC system for a year, the paper said.

They were finally expelled this past weekend.

DNC Chairwoman Debbie Wasserman Schultz said the party moved to fix the problem as quickly as it could and contacted a security company called CrowdStrike last month.

Wasserman Schultz told MSNBC that “from everything we call tell” the Trump files were the target.

CrowdStrike determined that two Russian intelligence agencies — possibly working independently — entered the DNC network in summer 2015 and April 2016.

Dmitri Alperovitch, the company’s chief technology officer, said one hacking group primarily monitored e-mail and chat conversations and may be working for Russia’s Federal Security Service, which was once headed by Russian President Vladimir Putin.

He said the second group was probably working on behalf of Russia’s military.

Opposition research files are routinely compiled by political parties to use against opponents. So-called “oppo” files are mostly made up of publicly sourced documents, news clippings and judicial filings, but can contain sensitive private and personal information.

The Russians also tried to gain entry to Hillary Clinton’s campaign, Trump’s campaign and various political committees.

Clinton told Telemundo she only learned of the breach when it was made public Tuesday.

“The Russian government uses cyber-attacks to gain information for economic commercial advantage, for political advantage, and for military advantage, and this seems like another example where they’re trying to vacuum up information,” she said.

Russia denied its government was involved.

“I completely rule out a possibility that the [Russian[ government or the government bodies have been involved in this,” Dmitry Peskov, a Kremlin spokesman, told Reuters in Moscow.

News of the DNC’s hack comes only days after WikiLeaks founder Julian Assange suggested there would be further problems to come for the Democrats.

“We have upcoming leaks in relation to Hillary Clinton,” he said Sunday.