Police investigating parcel bombs sent to Celtic manager Neil Lennon and two high-profile supporters of the club said another suspect package has been intercepted in Northern Ireland.
Officers are still looking for whoever was responsible for sending parcel bombs to Lennon, lawyer Paul McBride QC and former MSP Trish Godman.
The packages were designed to cause serious harm to the recipient, police said.
The latest package - believed to be a parcel bomb - was found at the National Return Letter Centre in Belfast, where mail which has not been delivered and has no return to sender address is retained by Royal Mail. It is the fifth package to be intercepted.
Strathclyde Police believe the package originally entered the postal system at around the same time as the devices that are already under investigation.
Officers from the Police Service of Northern Ireland recovered the package and alerted the Scotland force. A spokeswoman for Strathclyde Police said the latest find will be made safe and handed over to officers in Scotland for further investigation. It is understood the latest package was not addressed to a particular individual.
First Minister Alex Salmond said: "Everyone should remain calm in light of this new discovery and continue to give Strathclyde Police our full support in their investigation. Let's be quite clear - the individual or individuals responsible for these disgraceful actions will be apprehended and dealt with with the full force of the law."
The Police Service of Northern Ireland said it was alerted after the package was found at a postal sorting office in Belfast which handles returned mail from around the UK.
The item, found on April 12 at the National Return Letter Centre, had been returned undelivered from an address in Scotland. It is understood the parcel did not originate in Northern Ireland and had no links to the region.
Police said it was held at a secure location at Musgrave Street Police station in Belfast, while further inquiries were carried out. Army bomb experts have now confirmed it was "similar in nature" to the packages being investigated by Strathclyde Police. The PSNI said it would be liaising with Strathclyde Police and offered any assistance it could to help with its inquiries.