A Miami-Dade ethics commission investigation has found questionable absentee-ballot practices at a North Miami Beach assisted-living facility where three residents reported voting problems — and where, after a visit from investigators, one employee said she was instructed to toss all future ballots “in the garbage.”

The nine-month investigation began after Judith Thompson was turned away from the polls in last year’s general election after being told she had already voted absentee — though she had never requested a ballot. Two other women at the Park Plaza Retirement Residence also had trouble voting by mail.

No charges were filed as a result of the probe, initiated by the Miami-Dade state attorney’s office in January and completed by the Commission on Ethics and Public Trust last month.

The six-page investigation report found Thompson was denied her right to vote when someone else, with a different signature, mailed an absentee ballot in her name.

Two other incidents also revealed irregularities. Daisy Davis’ vote was rejected because the “X” signature on her absentee-ballot envelope did not match her signature. And Agnes Keyzer never requested or received an absentee ballot — though one was mailed to her after someone sent a request with a forged signature.

Earlier this month, Thompson urged Miami-Dade County commissioners to put teeth into the penalty-free ordinance that regulates absentee ballots. The commission is considering a measure imposing a $1,000 fine or 60 days in jail for breaking the law.

In a letter to Park Plaza administrator Gary Solomons, ethics commission Executive Director Joe Centorino cautioned against “unscrupulous practices.”

“We did not have enough evidence to file charges, but our review of voting records does indicate that all of the women had their ballots or related forms altered, forged or compromised,” he wrote.

Solomons could not be reached for comment Monday. He told investigators one candidate visited the ALF last year: state Rep. Daphne Campbell, a Miami Democrat who bought the residents lunch. But Campbell was elected in an August primary, the report noted, while the absentee ballots in question were for the November general election.

The report said it is unlikely that someone from outside the ALF could have tampered with the ballots without inside help.

“It is entirely possible that any fraudulent voter documents were prepared by persons linked to political campaigns and not by employees of the ALF; however, it would be difficult, if not impossible, for this to occur without access to the facility and its incoming mail,” it said.

According to the report, Solomons said he would be “astonished” if Latarra Kearney, the facility’s activities coordinator in charge of distributing mail, had acted improperly.

In an interview with investigators, Kearney said two candidates — one who bought residents lunch — campaigned at the ALF. She added that “she ‘does not recall at this time’ if she has ever filled out absentee ballots or forms requesting absentee ballots on behalf of residents.” Handwriting samples did not provide evidence of fraud by ALF employees.

However, Jennifer Prestol, the former receptionist in charge of receiving mail, said that Kearney had met with campaign workers — and that after Kearney was first questioned in January, Kearney instructed her “‘to dispose in the garbage all absentee ballots that arrive’ because ‘she didn’t want any more problems.’”

Centorino wrote that Kearney “should be strongly counseled that, were such behavior to take place, this could lead to a criminal complaint against her.”