Fourteen post boxes in a Birmingham suburb have been put out of use after thieves stole a van containing the keys to open them.
Royal Mail said the boxes in Hall Green would remain out of action for up to two weeks while replacement locks were ordered and fitted.
They are the second group of post boxes to have been put out of use in the city this month. A further 16 were sealed in Northfield after a set of keys was snatched from a postman on January 10.
A Royal Mail spokesman said delivery staff were being told to be on high alert after the thefts, which are been investigated by police to see if they are connected.
"It is fair to say that postmen and postwomen need to have a high level of vigilance at the moment because they have been targeted by thieves," he said.
Royal Mail blamed the long delay on a Scottish-based firm responsible for changing the locks. "Obviously it is very annoying for customers and we apologise to them," said the spokesman.
"We are trying to change the locks as soon as we can. I have been advised it could take some weeks because the specialist locks have to be ordered. We are tied to a single foundry for our boxes in Glasgow and the locks are part of that."
The Hall Green pillar boxes were closed after a delivery vehicle containing the keys was stolen on January 13.
Royal Mail said letters already inside were collected using a spare set of keys before they were sealed up.
Last night, one frustrated resident questioned the length of time it was taking to get the boxes back into use.
"Thank God they don't take that long to deliver letters," said George Kessack, aged 66 of Lakey Lane, Hall Green.
Royal Mail said there were alternative boxes in the area.