A staff member in An Post is under investigation following the alleged theft of letters and small parcels.

Gardaí have also confirmed they are looking into the incident that took place in the Dublin 12 area.

A number of undelivered letters and small packages have since been found following an extensive investigation and are being sent out to customers.

An Post has apologised to those affected and described it as a “serious service failure”.

"Rest assured"

A letter received from affected An Post customers said they “sincerely apologise that standard mail addressed to you was not delivered in a timely fashion”.

“While the investigation is ongoing, we are unable to provide any further information,” the letter read.

“However, please rest assured that the delivery of your mail, the full resolution of this unfortunate matter and the resumption of our top-quality delivery service remain our highest priorities.”

An Post has set up a dedicated phone line for anyone affected.

Delivery van and bicycle outside Glenageary An Post sorting office in Dublin Ireland. Image: Alamy