"Numerous instances" of illegal drone activity at Gatwick led to the airport being shut in the run-up to Christmas and it was not a police drone, according to Sussex's top officer.
Chief constable Giles York appeared to try to clarify earlier comments in which he said some of the drones spotted near the hub during the festive disruption may have belonged to police.
He said his force was using "all available resource" to identify and bring to justice those involved in the incident.
Officers are looking into "relevant sightings" by 115 witnesses, including 93 from "credible witnesses" such as a pilot, airport staff and police officers.
Police have searched 26 potential launch sites near the airport, but have not located the device that disrupted about 1,000 flights on 19 and 20 December.
The incident ruined the travel plans of more than 140,000 people.
Mr York said: "It is established that the incident, which led to widespread travel disruption, was caused by numerous instances of illegal drone activity at the site between 19 and 21 December. This was not a police drone.
"Police, supported by a range of partner agencies and working closely with Gatwick Airport, are currently examining relevant sightings by 115 witnesses – 93 from credible witnesses, people used to working in the busy airport environment, including a pilot, airport staff and police officers.
"This includes further information generated as a result of a public appeal for information and more than 1,000 house to house enquiries."
Two drones found near the airport have now been ruled out of the investigation.
Police previously said it was "possible" there was no drone at all – though they later backtracked.
Mr York told the BBC earlier on Saturday that he was "absolutely certain that there was a drone flying throughout the period that the airport was closed".
He said: "Of course, we will have launched our own Sussex Police drones at the time with a view to investigate, with a view to engage, with a view to survey the area looking for the drone, so there could be some level of confusion there."
He added that new military technology was in place in Gatwick to tackle rogue drones.
Gatwick Airport is offering a £50,000 reward for information leading to the arrest and conviction of those responsible.
Two people who were arrested over the disruption have now been released without charge.
Mr York said he was "really sorry" for the pair who said they felt "violated" after being questioned in custody for 36 hours before being freed.
But the chief constable said he was "convinced that the grounds for arrest – the lawful suspicion – in the first instance was well founded".
He added: "I'm really sorry for what he has experienced and the feeling of violation around it.
"I am really sorry for what he went through, but the reason why we held him was so that we could dispel everything in the first instance.
"What might have been worse as an experience for him would have been to be released under investigation still.
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"We are able to exhaust all our lines of inquiry on that first instance and, however hard it is, able to release him from police custody saying he is no longer a suspect in this line of inquiry.
"That's why we took the time – in order to allow him the best opportunity to put his life back on the rails."