A hacker from Ukrainian ‘hactivist’ group RUH8 is seen during an interview with Reuters in Kiev, Ukraine, Nov. 3, 2016. Reuters

While testifying in front of the Senate Intelligence Committee on Wednesday, Acting Director Samuel Liles, Department of Homeland Security’s (DHS) of the Office of Intelligence and Analysis Cyber Division, said the Russian government-linked hackers potentially targeted as many as 21 states' election systems last year. However, he said, there was no evidence of any votes being manipulated.

A second DHS official, Jeanette Manfra, the acting director of Undersecretary, National Protection, and Programs Directorate also backed Liles' testimony. When asked to identify the targeted states, she refused to do so citing confidentiality agreements, reports said.

Liles said a report published by the Office of Intelligence and Analysis in early October showed that DHS observed the "suspicious activities" on state government networks nationwide. It was later revealed that the "Internet-connected election-related networks, including websites, in 21 states were potentially targeted by Russian government cyber actors."

Read: Will Russia Hack Georgia’s Election?

However, what remains unclear is that why the Russian intelligence, after gaining access to state and local systems, did not try to disrupt the votes. One possibility could be that the U.S. warning was effective. Another former senior U.S. official, on condition of anonymity, agreed to discuss the classified probe into pre-election hacking. He said despite Russian hackers trying to meddle with the election systems for several months, they could not get through as the systems spread across more than 7,000 local jurisdictions, Bloomberg reported.

Liles, during his testimony, said the Intelligence Committee (IC) had constantly warned last year against Russian government being responsible for the "compromises and leaks of emails from U.S. political figures and institutions." He also told the Congress that the DHS had been receiving reports of cyber-enabled scanning and probing of election-related infrastructure in some states in August. Some of these reports appeared to have been related to Russian servers.

When Manfra refused to name the states whose election systems were tampered by the Russians, Mark Warner, a top Democrat on the Senate panel, expressed dissatisfaction.

Republican Sen. Marco Rubio too expressed concern, adding, as the investigation continued "it is important Americans understand how our voting systems work and communicate that in real time," reports said.

Arizona and Illinois last year confirmed that hackers targeted their voter registration systems, Reuters reported.

A report published by Bloomberg on June 13 said Russian hackers hit systems in 39 states, as told by a source who had direct knowledge of the U.S. investigation into the matter. In Illinois, investigators came across evidence that claimed cyber intruders tried to destroy voter data. Hackers got access to software which was designed to be used by poll workers Nov. 8. and also to a campaign finance database in one state.

Read: What Security Experts Hope To Learn About Russian Hacking From James Comey Testimony Hearing

Meanwhile, Russian officials publicly denied any role in cyber attacks related to the election last year, including a massive “spear phishing” effort that compromised Democrat Hillary Clinton’s campaign and the Democratic National Committee (DNC), among hundreds of other groups. Meanwhile, Russian President Vladimir Putin pointed out that hackers within Russia could have possibly been involved in the hack, however, they had no connection with the Russian government.