The election systems of 21 states in the United States were targeted by Russian hackers during the presidential race in 2016, a US Homeland Security official told the Congress on Wednesday, reported Reuters.

“We have evidence that election-related systems in 21 states were targeted,” Jeanette Manfra, the department’s acting deputy undersecretary of cyber security, told the Senate Intelligence Committee in a hearing on Wednesday. She said a small number of those systems were breached, but there was no evidence that any votes were manipulated.

Arizona and Illinois had confirmed in 2016 that hackers had targeted their voter registration systems. During the hearing, Mark Warner, the top Democrat on the Senate panel, expressed his frustration at Manfra’s refusal to identify which states had been targeted.

The US House Intelligence Committee is investigating the alleged Russian role in the 2016 presidential elections. Russia has repeatedly denied the allegation of orchestrating cyber attacks during the polls. US President Donald Trump has also dismissed claims that his campaign associates had colluded with Moscow.

Moreover, Jeh Johnson, who was the head of the Homeland Security Department in the Barack Obama administration, said his office had issued warnings about hackings into voter registration databases. He told the committee that the warnings did not get the attention he would have liked and blamed the emergence of a 2005 tape, where Trump bragged about sexually assaulting women, for distracting the American public.

When asked why the Obama administration did not do more to warn the public, Johnson said, “We were very concerned that we would not be perceived as taking sides in the election, injecting ourselves into a very heated campaign.”

On June 16, Trump had confirmed that he was being investigated for his alleged role in Russian meddling into the US election in November 2016. The Republican had called it a “witch hunt” and said that even after seven months of investigations, nobody had been able to prove that he had colluded with Russia. However, his lawyer Jay Sekulow said on June 18 that the president was not under investigation in the case.

Earlier, former FBI Director James Comey had stated before the US Senate Intelligence Committee that he was certain he was fired because of the president’s concerns about the Russia investigation.