Police have launched a series of dawn raids and detained two people in connection with the mail bombs posted to Celtic boss Neil Lennon.
A 41-year-old man and a 43-year-old man were taken into custody under the Explosive Substances Act.
They were swooped on by officers at two addresses in Ayrshire.
Following the raids at 6am, forensics officers searched the second house and sniffer dogs were sent into a black Ford Focus parked outside.
Strathclyde Police chief superintendent Ruaraidh Nicolson said: “The enquiry is doing well, we’ve got two people detained.
“They are at this moment in time being interviewed by police officers nearby.
“I would like to reassure the public there is no risk to them, we are fully in control of the situation at the addresses in the area and we will maintain that and make sure that people in the vicinity are safe.”
The police chief said the two men were in no way connected to the pitch attack on Lennon at Wednesday’s match against Hearts at Tynecastle in Edinburgh.
A man has already been detained in connection with the attempted assault.
Chief supt Nicolson said the “substantial” police swoop had taken a great deal of planning over a few days.
It follows a major and high-profile police investigation into intercepted bombs which were posted out to Celtic boss Lennon, his lawyer Paul McBride QC and former MSP Trish Godman.
Strathclyde Police said the two packages sent to Lennon, and the two others, in March and April were “designed to cause real harm to the person who opened them”.
A fifth suspect package, addressed to the offices of Cairde Na H’Eireann (Friends of Ireland) in Glasgow, was also intercepted by officers last month.
The raid is the first breakthrough in the operation. It has taken in people who posted letters at the mailbox in Kilwinning where one suspect parcel was found.
Police have spent days stopping passers-by in the street and appealed for help from a couple who boarded a Stagecoach bus close to the postbox on April 15.
In addition to the two men taken into custody, officers yesterday took away a number of others who were yesterday helping with their inquiries.
Neighbours in the small Ayrshire towns have been left stunned by the raids.
At one address in Innerwood Road, Kilwinning, where officers broke down a door to gain entry to a house, a neighbour said: “About ten past six it started this morning, I heard the bang of the door coming down.
“It woke me up and that’s when I saw the police. I saw a man come out in handcuffs.
“The weans came out and then the police walked some other people down the road.”
Lennon, 39, has endured threats and abuse throughout his career and was forced to retire from representing Northern Ireland in international football after claiming he had received death threats from a paramilitary group.
He and his family are under 24-hour police protection.
Mr McBride is a well-known Celtic fan and on her final day as MSP for West Renfrewshire, Ms Godman was pictured wearing a Celtic football top at Holyrood.