Election officials in Texas' largest county say they have already cleared about 18,000 voters in the Houston area who the state had wrongly flagged as potential non-citizens.

Harris County special assistant attorney Douglas Ray said Wednesday he expects to find more mistakes as the state backpedals on claims that tens of thousands of illegal ballots had potentially been cast since 1996.

Texas Secretary of State David Whitley said last week that roughly 95,000 voters matched records of noncitizens who had obtained state IDs.

Republicans seized on the announcement to renew claims of widespread voter fraud.

But the numbers began unraveling Tuesday. That's when local officials say Whitley's office revealed to them the list was flawed.

Democratic lawmakers said they'll investigate. Whitley has not publicly acknowledged any error.