Forty-six states have requested that the Department of Homeland Security help them fortify their voting systems against hacks, CNN reported Monday.

An unnamed senior DHS official told CNN that all but four states have requested this federal assistance. It was not clear from the report which states have not reached out for help. That number is up from 33 states earlier this month.

Experts have repeatedly said that it would be extremely difficult to hack the U.S. election. But the recent hacks of Democratic political organizations like the Democratic National Committee and Hillary Clinton campaign officials’ emails, as well as fears of a “rigged” election stoked by Donald Trump, have put the public on high alert.

CNN reported more than 20 states have experienced hacking attempts on their voting systems, but only one one has been confirmed successful. A hack in Illinois reached data on about 90,000 voters, but no alterations to that data were detected, according to the report.

These kinds of hacks are attractive for accessing voter information that can be useful for financial crimes, CNN reported.