Police investigating parcel bombs sent to Glasgow Celtic's Irish-born manager Neil Lennon are appealing for a couple in their early 20s to come forward.
The couple were seen in the Scottish town of Kilwinning in Ayrshire on the day the most recent explosive device was discovered there. Two prominent Celtic supporters were also sent parcel bombs.
Scottish police have also arrested two men suspected of posting sectarian and racist comments on the internet.
The two men were charged with sectarian breach of the peace on Saturday and dozens of others are being investigated.
Lennon, from Lurgan in County Armagh, has had sectarian threats made against him throughout his career as a player and manager at Celtic.
Last year, along with Celtic's Northern Ireland-born players Paddy McCourt and Niall McGinn, he was sent bullets in the mail, while in 2002 he hung up his boots on his international career after a death threat was made against him by loyalists, this before a Northern Ireland game.
The latest developments came just days before Celtic's crucial league game against bitter rival Rangers. The game on Sunday ended 0-0 with Celtic now trailing Rangers by a point but with a game in hand as the league championship race enters its final month.
Scottish police had drafted in an extra 1,000 officers into Glasgow for the game fearing trouble in the city during match day. Nine arrests were made but overall the game passed without major incident.