PSNI Chief Constable Simon Byrne has confirmed the 'New IRA' bomb discovered in Creggan this week was not the sole target of the operation that saw the deployment of 80 police officers to the estate on Monday.
Chief Constable Byrne said it was possible other bomb-making equipment and devices were still being concealed in the area.
Speaking in the Strand Road barracks on one of his first visits to Derry in his role as the new PSNI boss, he said: "We made an assessment and launched a policing operation to deploy extra resources into the Creggan looking for explosives and weapons."
He added: "There could always be more devices, that's the unknown question isn't it."
Mr. Byrne refused to be drawn on the provenance of the commercial explosives contained in the bomb discovered in Creggan Heights on Monday night.
"I'm not going to go into detail about what was in the bomb. The investigation is progressing as I'm stood here," he said.
But he said he was concerned that with the attempted deployment of a vertical mortar type weapon in Strabane at the weekend and a Command Wire Initiated Improvised Explosive Device in Creggan, violent republicans were demonstrating a greater degree of sophistication in their attempts to murder police officers.
"Over the last few months I've dealt with more attempts or threats to kill my officers since I've been here than my predecessor dealt with in a whole year.
"What we've seen is changing types of engineering capability that shows that determination and motivation to launch attacks that are clearly aimed at killing or maiming our officers but are also indiscriminate and, in any one of these situations, potentially a member of the public or passing family could have been killed.
"The device that we recovered here was clearly potentially a very dangerous device. I've little doubt had it detonated anyone nearby would have been killed and seriously injured tens of metres away because of the way it was put together. It was complex and it was sophisticated and that threat is clearly changing," he said.
The Chief Constable said the bomb-making expertise demonstrated by the 'New IRA' could as easily have been gleaned from the internet as from veteran republican explosives experts or engineers.
"I think the expertise is coming perhaps from the past. There's no secret that the internet is buzzing with information on how to make explosive devices and we are working hard, both with specialist trained detectives we have here but also with other agencies, to see how best we can thwart and frustrate that crime," he said.
As to whether former members of the so-called 'Provisional' IRA may now have become active within the 'New IRA', he said: "I'm not going to put labels on particular associations. I think you've got to keep an open mind."
Chief Constable Byrne was clear, however, that the PSNI would struggle to deliver a normal policing service in face of the continuing high level of threat from violent republican groups without more resources.
"We can't keep working at the pace we have done across the summer dealing with the rise in this type of attack as well as day to day policing issues.
"I've been very clear that we need to grow the PSNI to that figure of 7,500 officers so that we can push more police officers to work with communities to get more information, to deal with day-to-day crime, but also continue their fight against paramilitaries and terrorism that coerce other people to attack us."