Police in Northern Ireland said on Tuesday they had recovered four suspected pipe bombs from a cemetery in Creggan near Derry, Northern Ireland following a public safety operation.
The discovery comes hours before U.S. President Joe Biden is due to arrive in the country.
"The discovery of these devices was a further sinister and worrying development," Assistant Chief Constable Bobby Singleton said in a statement.
Biden arrives in Belfast late on Tuesday at a delicate political time in Northern Ireland as he helps mark the 25-year anniversary of a peace deal that largely ended 30 years of bloodshed there.
Police said the operation in the cemetery is now complete and police officers have left the scene.
"Colleagues from Terrorism Investigation Unit will now lead on this investigation," Singleton said.
