Templemore Sports Complex has been evacuated following the discovery of a suspicious object.
Police say Army Technical Officers have been tasked to the scene.
Last week the complex - used as an election count centre - was evacuated as votes were being counted and a controlled explosion carried out after a viable device was discovered in a hijacked car left in the complex's car park.
SDLP councillor Mark Durkan said a group of school children were among those evacuated this afternoon.
"Those responsible for planting this device have once again caused great distress and fear – especially for the local schoolchildren who had to be evacuated from the swimming pool.
"Children had to be taken back to school with their clothes still in the building.
"The victims today have been schoolchildren. The other night they were old-age pensioners. Those responsible have clearly shown they do not care about those who suffer as a result of their actions.
"I would also like to take this opportunity to praise the Templemore Complex staff who have had go through this traumatic ordeal twice now in the past few days."