A workman cutting a hedge at a County Antrim school escaped injury when a bomb fell at his feet, the principal has said.
School principal Lesley Meikle is furious lives were put at risk
Lesley Meikle said she did not believe Harryville Primary School in Ballymena was the intended target but is furious lives were put at risk.
The school's 142 pupils were moved out while the device was defused.
It is not being linked to the recent discovery of pipe bomb parts. Further suspect devices have also been found.
Mrs Meikle said maintenance men from the local education board were at the school, in the Casement Place area, when the incident happened at 0900 BST on Tuesday.
"They were cutting the hedges for me and it fell out on one of the men that were cutting. Thankfully it didn't go off. That was a blessing.
"We were taking children on the way to swimming when the workmen came down and told us to stop as they thought they had another suspicious device."
She hit out at those who left the device in the area, saying: "How dare they endanger children's lives?
"This is the second time. It is absolutely disgusting, despicable. Who do they think they are?"
'In the frontline'
The police said they did not think the school was the target and condemned those who left the bomb parts.
A PSNI spokesman said: "It was reckless in the extreme to abandon items of this nature close to a school, where they might have been found and handled by children."
DUP leader and North Antrim MP Ian Paisley said he sympathised with the principal, staff and the caretaker of the school.
"They realised that both they and the children were in the frontline," he said.
"After visiting the school in the immediate aftermath of the discovery, I was struck with the courage and determination of all not to panic but to face the situation with a calm determination and an unbroken spirit."
Children at the school were sent home for the day
Ulster Unionist Assembly member the Reverend Robert Coulter said it was a miracle the device did not explode.
"Attacking innocent children is the lowest of the low and the full force of the law must be brought to bear on those responsible," he said.
Sinn Fein North Antrim assembly member Philip McGuigan said he was concerned at the discovery.
"This clearly is another indication that unionist paramilitaries in north Antrim are intent on creating difficulties and dangers for the community in this area.
"To leave these deadly devices in public is worrying, but I would have to ask what these people thought they were doing when leaving these things on the premises of a children's school."
On 12 September, three viable pipe bombs were found in the Harryville area.
A follow-up search of the area is now under way, and the school has been closed for the rest of the day.