The Ohio governor's website was still down for maintenance at 17:30 local time (21:30 GMT).
Several other Ohio government websites were hacked, including those of the state's first lady Karen Kasich, as well as the Ohio Department of Rehabilitation and Corrections, the Department of Medicaid, and Casino Control Commission.
The Ohio governor's website wasn't loading on Sunday afternoon, and a cached version showed the message "hacked by Team System Dz".
Websites belonging to a Long Island town and the OH state government were hacked Sunday to broadcast ISIS propaganda, according to reports.
Kasich's staff said it was aware of the hack and is working to resolve the issue, CNN reported.
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Tom Hoyt, chief communications officer for Ohio's Department of Administrative Services, was among OH officials who confirmed the hack.
Authors of the website "Cryptosphere", which tracks hackers worldwide, have detailed dozens, if not hundreds, of similar hacks in recent years by the so-called Team System DZ, which they called a "pro-ISIS hacker crew" and claim are based in Algeria. The New York Post reported that the same message was also used in the hacking of the Brookhaven, Long Island homepage. The websites are expected to run sometime Monday, he told the Associated Press.
The websites in OH hacked with the message also include that of first lady Karen Kasich.
Other sites the have been hacked on Sunday, according to the the hacker's Facebook page.
It was not immediately clear who the group was or whether it was genuinely affiliated with ISIS.