Officers remain at the scene of the security alert in the Corrody Road area.
Police and Ammunition Technical Officers attended the scene following the discovery of a suspicious object on Saturday, February 18.
The device has now been taken away for further examination.
Derry City and Strabane Area Commander, Chief Superintendent Nigel Goddard said: “A number of cordons remain in place as police continue to search the area as part of our investigation.
“We would like to thank the local community for their patience and understanding during this time.
“This explosive device was recklessly left in a public area, just metres away from houses and a sports area where a number of children were playing football.
“Four people have been arrested and a number of searches have been carried out by detectives investigating this incident and an attempted hijacking on Friday evening.
“They remain in custody assisting us with our enquiries.
“Our focus remains firmly on keeping people safe against the threat posed by violent groups.
“No matter what level of involvement people have with any criminal or terrorist activity, we will investigate and where appropriate, put people before the courts to answer for their actions.
“Our investigation into this incident is ongoing, and we strongly urge anyone with information, suspicions or concerns about dangerous and illegal activity in our community to contact us on 101.”
A report can also be made using the online reporting form via www.psni.police.uk/makeareport
Alternatively, information can be provided to Crimestoppers anonymously on 0800 555 111 or online at www.crimestoppers-uk.org
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