Detectives are investigating a number of threatening letters received by post offices in east Lancashire.
The letters, which contain racist content, were received yesterday at post offices in Burnley, Padiham and Pendle.
They are being linked to letters which were received by post offices across Lancashire last year.
Lancashire Police say they have reviewed the letters and are speaking directly with the those affected. But they say there is not thought to be any direct threat to any individuals or the wider community.
Detective Inspector Andy Horne said: “We understand that this may cause concern and we want to assure people that we are working closely with the post offices involved to ensure the safety of staff and customers."