A brick was used to smash the front window of a property at Carnany Park in Ballymoney sometime overnight, and the device was then thrown inside.
Detective Sergeant Leighanne Miller said: “The residents discovered the broken window and the item in their living room at around 8.30 am this morning.
“Police were alerted and when ATO examined the device they found it was an elaborate hoax.
“It has now been removed for forensic examination.
“While the security operation was ongoing, it was necessary to evacuate a number of nearby homes as a safety precaution.
“This obviously caused disruption to the weekend routine for many families and older people.
“We are working to establish a motive for this incident and we are appealing for anyone with information to please get in touch with detectives in Coleraine by calling 101, quoting reference number 316 14/04/18.”