A US federal probe found that reported foreign meddling and hacking attempts had “no material impact” on the midterm congressional elections last year.

The statement on Tuesday by the US Department of Justice and Department of Homeland Security did not confirm various reports from state and local security officials during the campaign that foreign actors tried to break into voting systems and databases in multiple states.

“There is no evidence to date that any identified activities of a foreign government or foreign agent had a material impact on the integrity or security of election infrastructure or political/campaign infrastructure used in the 2018 midterm elections,” the two departments concluded after reviewing a summary of a classified report.

During a UN Security Council meeting in September, US President Donald Trump accused China of meddling in the then-upcoming midterm election.

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Some state and local governments reported attempts to access their networks ahead of the November 2018 election, Reuters reported, but US officials said they were able to prevent or limit access.

On the night of the November 6 election, Homeland Security Secretary Kirstjen Nielsen said there were no signs that voting systems had been breached.

Democrats won control of the House of Representatives following the midterm election.

2016 election meddling

The US government intensified its scrutiny of the vote after concluding that the Russian government ran a concerted operation during the 2016 presidential campaign to hack into political party computers and voting systems and to influence voters via social media disinformation.

While voting systems were not significantly impacted during 2016, US intelligence said that the social media campaign and the hacking of Democratic Party computers bolstered Trump’s presidential campaign.

US prosecutors are investigating whether Trump’s campaign worked with the Kremlin to win the 2016 election. Trump has denied any collusion and Moscow has also denied involvement.

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Last September, Trump signed an executive order authorising sanctions against individuals or countries found to have meddled in US elections.

The 2016 election also illustrated how hackers can compromise candidates by releasing internal emails and other sensitive documents and by working to sway public opinion through social media.

Ahead of the November 2018 election, US intelligence and law enforcement officials warned that foreign actors were continuing their manipulation efforts. Prosecutors charged a Russian national with participating in a Kremlin-backed plan to interfere in the election.

Congress approved $380m last year to help safeguard voting systems and federal officials worked with the state and local governments that administer elections to limit their exposure to interference.

US security officials have said that they foresee a potent interference threat from foreign governments, including Russia, China and Iran, in the 2020 presidential election.

Security experts have warned for years that US election infrastructure – voting machines, voter registries and other computer systems – could be manipulated to change vote tallies or prevent people from casting ballots.