Colorado Secretary of State Scott Gessler says 300 more suspected noncitizens have been found on the state's voter rolls.

They were among more than 3,900 people who received letters in August questioning their citizenship.

Gessler's office previously said another 141 people who received letters appeared to be noncitizens, based on a federal immigration database.

Elections officials did additional checks after obtaining more immigration identification numbers to run through the database.

Gessler, a Republican, said Tuesday that he wants "to ensure the most accurate, reliable elections possible."

It's the latest chapter in a contentious national debate over whether noncitizens are illegally registered to vote. Critics say the checks could disenfranchise eligible voters.

Gessler says he forwarded the names to county clerks for any potential challenge at the polls.