The Ministry of Defence said today the Royal Military Police are working with police in the investigation. It declined to provide details on the suspect.
Greater Manchester Police say a 19-year-old man was arrested on Monday in connection with the discovery of the device at a house last week.
Neighbours were evacuated, and bomb disposal officers were called to remove the device from the scene.
The soldier, who is based in Germany, was flown to Britain for questioning by police before he was released on bail yesterday.