The contract postal worker, 46, has been charged with three offences after a joint operation, involving police and Australia Post, resulted in her allegedly caught in the act of stealing from a birthday card.

The woman has been charged under federal law with the theft of mail, tampering with mail and delaying mail.

Detective Sen-Constable Jason Williams, of Cobram police, said a probe was launched about a month ago after reports from the Yarrawonga, Bundalong and Burramine areas that birthday cards had gone missing.

He said some residents of Bundalong had noticed something amiss with cards for up to 12 months.

At least 12 victims have been identified, but Sen-Constable Williams said it was unclear how many more might be affected and he urged those who think they might be to contact police.

Sen-Constable Williams said the total amount of money involved was also unconfirmed with the most common thefts involving $20 and $50 notes as well as scratch lotto cards.

“How many grandkids are thinking to themselves ‘I didn’t get anything from nanna this year?’ and vice versa, how many grandparents are thinking ‘Gee I sent $50 to little Johnny and I haven’t even got a thank-you’?” he said.

“There would be plenty of broken hearts out there.

“To prevent it, just don’t send money in the mail.”

Australia Post media and communications manager Mel Ward said the woman, whose job involved delivering mail to areas surrounding Yarrawonga, was no longer employed by the agency.

“Theft of mail and tampering with mail is a federal offence, and Australia Post has zero tolerance to breaches of mail security,” Ms Ward said.

“We take these incidents very seriously, and any person implicated in such activity is immediately terminated from employment.”

Ms Ward said that theft of mail was “rare” and Australia Post had devised security methods to prevent items being tampered with by employees.

“Australia Post recommends customers do not send cash in the mail and instead use money orders which offer more security and peace of mind,” she said.

The woman will be summonsed to appear at Cobram Court on a date to be fixed.