The names of more than 118,000 registered voters were left off the rolls in Los Angeles County because of a printing error, according to election officials.
That error affected roughly a third of the county's 4,357 precincts during the California primary on Tuesday.
Voters whose names were not on the roster were supposed to be given a provisional ballot. But verifying and counting all those provisional ballots could delay some vote counts in the state.
In California's so-called "top-two primary," the top two vote getters advance to the general election in November regardless of their party affiliation.
Officials in Los Angeles County said they're working to figure out the root cause of why some voters' names were not included on the rosters.
Additional reporting from Newsy affiliate CNN.