WASHINGTON — The Senate Intelligence Committee released a bipartisan report Thursday on Russian election interference that found the U.S. election infrastructure was unprepared to combat “extensive activity” by Russia that began in 2014 and carried on at least into 2017.

The report was issued just one day after former special counsel Robert Mueller warned U.S. lawmakers that he believes Russia will seek to interfere again in the 2020 campaign and that “many more countries” are also developing similar capabilities.

“In 2016, the U.S. was unprepared at all levels of government for a concerted attack from a determined foreign adversary on our election infrastructure,” Sen. Richard Burr, R-N.C., chairman of the Senate Intelligence Committee, said in a statement.

The 61-page report — based on interviews with state election officials, Obama administration officials and government and intelligence community officials — is just the first volume of the findings of the committee's investigation. It includes eight pages of recommendations to shore up the country’s election infrastructure to prevent future interference.

The report found that the Russians took advantage of the nation's decentralized voting system, “exploiting seams” between federal oversight and state election systems. It also found that election cybersecurity was “sorely lacking” in 2016 and that federal attempts to warn states about potential security breaches "did not provide enough information or go to the appropriate people."

Election databases weren’t as secure as they should be, according to the report, and aging voting machines with no paper trail were vulnerable.

For instance, in one state, which was not named but identified as “state 7,” the password to the machine was as simple as “ABC123” and the people testing the machines could easily switch the machines into supervisor mode and tamper with the votes to “call the results into question.”

The communication between the Department of Homeland Security to the states in 2016 was insufficient and lacked context, the report notes. Twenty-one states said they found out about possible interference from the media or the Intelligence Committee’s hearing on the topic in 2017.

But the committee found no evidence that any votes were changed or that voting machines were manipulated.

The report also says that significant investments, including $380 million in grants to states to bolster cybersecurity and replace voting machines, helped secure the election system, but added that more is necessary.

The report echoes testimony by Mueller before the House Intelligence Committee on Wednesday, in which he said Russian interference in the election was significant and that the Russians are actively working to undermine the 2020 elections.

“There’s still much more we can and must do to protect our elections,” Sen. Mark Warner, D-Va., the top Democrat on the committee, said. “I hope the bipartisan findings and recommendations outlined in this report will underscore to the White House and all of our colleagues, regardless of political party, that this threat remains urgent, and we have a responsibility to defend our democracy against it.”

The committee recommends that states purchase more secure voting machines, including voting machines with a paper trail. It recommends audits of voting machines and security audits.

It also suggests that election cybersecurity needs to be a bigger national priority and that the United States should communicate to other world leaders that an attack on U.S. elections would be seen as a hostile act.

While the U.S. expelled Russians in the past for election meddling, President Donald Trump has been reluctant to acknowledge Russian interference. In a bilateral meeting with Russian President Vladimir Putin in June, Trump was asked by a reporter if he would tell Putin not to meddle in the elections. Trump said, “Yes, of course, I will,” before turning to Putin and saying, “Don't meddle in the election, President. Don't meddle in the election.”

Despite saying that Russia took advantage of the decentralized elections in the U.S., the report affirms that states should remain in the lead of running elections. Sen. Ron Wyden, D-Ore., wrote that he couldn’t support the recommendation because it doesn’t support centralizing the oversight of elections. He also supports national standards for voting machines, which the report does not endorse.

While the report was bipartisan, any federal legislation to shore up election security could quickly become partisan. Senate Democratic leader Chuck Schumer attempted to bring up an election security bill in the Senate on Thursday but the effort was blocked by Republicans.

The subsequent volumes of the committee’s investigation will cover the intelligence agencies’ assessment of Russian interference, the Obama administration’s response and the role of social media disinformation campaigns.