Gardaí investigating a bomb scare at the Intel plant in Co Kildare have traced the phone used by the caller to ring in the threat.
The man at the centre of the alert used a public phone in Balbriggan, north Co Dublin, early this morning.
Gardaí are now focused on gathering CCTV footage capturing the area around the time of the call in a bid to identify the caller, who claimed to represent Islamic State.
The search will also include cameras fitted on public transport vehicles.
Garda sources said it was impossible to determine at this point if the caller was representing Islamic State or a lone sympathiser aiming to disrupt a major US company in Ireland.
“We could also be dealing with somebody who thinks a call like this a good prank,” said one official.
The man who placed the call to the Garda control and command centre at about 5.30am stayed on the line for a very brief period.
He claimed he was from Islamic State and that there were 10 bombs at the US computer chip maker's Leixlip plant.
Garda sources said they were taking the threat seriously, especially in light of the terrorist attacks in Paris last week carried out by Islamic fundamentalists.
Intel said in a statement: “Shortly after 6am this morning gardaí received what they believed to be a credible threat identifying Intel in Leixlip as the location of that threat.”
“As per normal protocol gardaí shortly thereafter coordinated a response with Intel.
“A controlled evacuation of the site followed and a search was conducted by trained Intel security personnel throughout the campus, with the buildings being declared safe just after 8.30am.”
A large Garda team also conducted a search of the plant which employs an estimated 4,000 people.
That operation was coordinated by Supt Gerry Wall at Leixlip garda station. The Special Detective Unit, which investigates terrorism, was also involved.
After two hours of searching, no threat was detected and the area was declared safe.
There were very significant traffic delays in the area due to the Garda cordon put around the plant to ensure the safety of the public in case of explosions at the plant.