Royal Mail workers are being quizzed after a sack containing dozens of Christmas gifts was ransacked and thrown onto a railway line.
The sack was found by railway workers clearing leaves in Sutton Coldfield, West Midlands.
Children's presents addressed to Canada were among those ripped open or stolen, before the debris was thrown away.
Royal Mail is carrying out an internal investigation to find out who was responsible for the theft.
Gifts and notes
A Winnie The Pooh calendar and a baby's bib were among the collection of presents which were not stolen by the thief.
One of the workers, who passed the bag onto police, said: "We were spraying chemicals to remove leaves from the track when we noticed the bag.
"It is terrible because I am a Royal Navy reservist and I know just how important it is to get this stuff.
"There were some personal gifts in the bag with notes, but there were also parcels that had clearly been opened, the contents had been opened and the packaging was left."
'Not a postman'
The same sorting office was probed by Royal Mail investigators and a fraud team after the alleged theft of bank cards and cheque books in August.
Royal Mail spokesman Dan Panes said: "Security around the sorting office is always high, but we will see if there is any areas which can be improved.
"We are working closely with the police, but it is too early to say how this has happened because it is still very early in the investigation.
"The likelihood is that this was not a postman, because there are none at the sorting office and this was a load that was not marked for delivery."