A pipe bomb was made safe by the bomb squad in the Altnagelvin area on Sunday.
The device was recovered during a security alert in the Gelvin Gardens area.
A number of residents were moved from their homes while police and ATO examined the device which was found at around 5pm.
Detective Sergeant Brian Reid said: ”The device was made safe and has been seized for forensic examination.
“Detectives from Strand Road Reactive and Organised Crime are now investigating this incident and we would like to speak to witnesses or anyone with information.
“We are especially keen to hear from anyone who noticed any suspicious vehicles or people in the area at any time on Sunday, March 6.
“The number to call is 101. Or, if someone would prefer to provide information without giving their details, they can call Crimestoppers anonymously on 0800 555 111.”