WASHINGTON (AP) -- Hackers have made their way into state election systems "in a few cases," but the federal government hasn't found "any manipulation" so far of voting information, the Homeland Security secretary said Saturday.
Twenty-one states have contacted the agency for help in safeguarding their election systems, and Jeh Johnson is urging additional requests for cybersecurity assistance.
"We hope to see more," Secretary Jeh Johnson said in a statement.
A department official told The Associated Press on Friday that hackers have targeted the voter registration systems of more than 20 states in recent months. The official, who was not authorized to publicly discuss the subject and spoke on condition of anonymity, said it was unclear whether the hackers were foreign or domestic.
As the Nov. 8 vote nears, there are heightened concerns that foreign hackers might undermine voter confidence in the integrity of U.S. elections. Federal officials and many cybersecurity experts have said it would be nearly impossible for hackers to alter an election's outcome because election systems are decentralized and generally not connected to the internet.
"We must remain vigilant and continue to address these challenges head on," Johnson said. "These challenges aren't just in the future. They are here today," Johnson said.
The FBI last month warned state officials of the need to improve their election security after hackers targeted systems in Illinois and Arizona. FBI Director James Comey told lawmakers this past week that the FBI is looking "very, very hard" at Russian hackers who may try to disrupt the U.S. election.
Johnson said that in recent months, "malicious cyberactors have been scanning a large number of state systems, which could be a preamble to attempted intrusions. In a few cases, we have determined that malicious actors gained access to state voting-related systems. However, we are not aware at this time of any manipulation of data."
He gave no specifics.
The FBI held a conference call on Friday with the local officials who run elections in Florida, according to a spokeswoman for Secretary of State Ken Detzner. A person who was on that call said authorities had seen evidence of someone probing a local elections website. The person was not authorized to publicly discuss the call and spoke on condition of anonymity.
Hackers also tried to mine data from the Arizona and Illinois voter registration systems, according to Kay Stimson, a spokeswoman for the National Association of Secretaries of State. She said in Arizona a hacker tried to probe voter registration data, but never infiltrated the system, while in Illinois hackers got into the system, but didn't manipulate any data.
Associated Press writer Gary Fineout in Tallahassee, Florida, contributed to this report.