After more than a week of forensic analysis, cybersecurity investigators found no signs of hacker infiltration into the state's voter registration database and have brought the system back online, the Arizona Secretary of State's Office announced.

The system was taken offline for nine days after the FBI found a "credible and serious" threat to the database, which contains personal information about the more than 3 million registered voters in the state. The system was restored Thursday.

READ: Was Arizona's voter database hacked? FBI says maybe

"We have not found any evidence of malware or command and control software in the voter registration system and have restored its use," Secretary of State Michele Reagan said in a statement. "Voters can check their registrations and EQUAL users can continue to collect $5 contributions. We have implemented measures to ensure that access to the system is secure. For these reasons, we believe it is safe and prudent to turn the system back on and continue its use."

The registration database was initially taken offline June 28 for examination, Reagan said in a statement. State cyber experts took immediate steps to investigate the issue, said Arizona Secretary of State's Office spokesperson Matthew Roberts. After the FBI identified a threat, cyber teams found malware on a county election official’s computer. However, the nine-day scrub turned up no evidence of malicious software in the voter registration system itself, according to Thursday's statement.

The voter registration database contains the name, home address, date of birth and party affiliation of the more than 3 million registered voters in the state of Arizona. It includes the last four digits of each voter’s Social Security number, his or her driver’s license number and a photograph of his or her signature. The database also contains phone numbers and email addresses of voters who choose to share them, Roberts said.

"We apologize for the inconvenience; however the integrity of the system itself is extremely important," Reagan said.Copyright 2016 KPHO/KTVK (KPHO Broadcasting Corporation). All rights reserved.

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