Potential voter fraud is under investigation in Denver and Adams County after election officials identified “ballot irregularities” and mismatched signatures coming from a Denver adult day care.

The ballots, which had suspicious issues with the voter signatures, all came from the same day care address, Denver Clerk and Recorder Paul Lopez said in a statement.

Lopez said his team notified the Colorado Secretary of State’s Office, the Denver District Attorney’s Office and law enforcement in multiple counties about the potential fraud.

Ballots from the Denver adult day care were sent to multiple counties, according to Lopez’s statement, but information about the number of fraudulent ballots and which other counties were involved was not available due to the ongoing investigation, election officials said. The address of the day care was not released on Tuesday.

Denver District Attorney spokesperson Matt Jablow confirmed Tuesday the DA’s office is investigating the incident.

The 17th Judicial District Attorney’s Office is investigating three voter fraud allegations in Adams County related to ballots from the Denver incident, director of communications Chris Hopper said.

“This incident demonstrates how Colorado’s multi-layered ballot processing systems have been proven effective in identifying irregularities in voted ballots, assuring voters Colorado elections are safe and accurate,” Lopez said.

The Denver incident comes nearly two weeks after at least a dozen Colorado ballots were stolen and fraudulently filled out in a Mesa County election scheme.

Authorities detected the scheme ballots before most of the ballots were processed, Colorado Secretary of State Jena Griswold said, but three were successfully cast after clearing the signature-review process. A fourth ballot nearly made it through, but it was flagged after the legitimate voter received a notification that their ballot had been cast.

Confirmed voter fraud is rare in Colorado’s nearly all-mail voting system, which has multiple safeguards and checks to detect improper voting.

When the Mesa County scheme was revealed, Griswold said another ballot issue was under investigation elsewhere in the state. It’s not clear if the Denver investigation is related.

Election fraud involving voter impersonation is punishable by a fine of up to $5,000 and jail time of up to 18 months.