The caravan was discovered on the side of a road in Dural on January 19 by a member of the public, who alerted police.

The investigation was only made public yesterday.

The explosives the caravan contained were said to be capable of causing a “mass casualty event”, police said, and there were indications they were intended for use in an antisemitic attack.

Several arrests have been made but police say they are on the “periphery” of the investigation.

At least 100 officers from multiple agencies, including the Australian Federal Police and ASIO, have been assigned to the investigation.

Speaking to Ben Fordham on 2GB, NSW Police Deputy Commissioner David Hudson said there were more arrests to be made.

“Until you charge everybody involved there is the potential for incidents to occur,” he said.

He said police were trying to trace the source of the explosives, which consisted of Powergel, used “almost exclusively” in the mining industry.

NSW Premier Chris Minns said he could not “responsibly” assure the community the threat was over.

“I would love to give assurances that the threat has passed … but I can’t do that,” he told Today.

Speaking on Today, former NSW Police officer and terrorism expert Peter Moroney said there were multiple reasons police would have kept the investigation a secret until yesterday.

“As (NSW Police) Deputy Commissioner (David) Hudson explained in his press conference, police will often not put out information on the pure point of remaining in a tactical or strategic advantage over the criminals or the criminal syndicates that we’re working,” he said.

“We don’t want to advertise what we know or don’t know, so that’s certainly not unusual.”

Moroney said the explosives, which are understood to have been reported stolen from a mine site, should be easy to track.

“The problem might be, for example, if it was stolen, say 12 months ago, we’ve got a 12-month black hole where we simply just don’t know where those explosives have been, or potentially going towards what state they are being transferred into before they become an actual explosive itself,” he said.

Minns has unequivocally described the incident as one of “terror”, while NSW Police have confirmed they are treating it as a terrorist act.

Co-CEO of the Executive Council of Australian Jewry, Peter Wertheim, told Today the operational police need for clandestine investigations needed to be balanced against the public’s right to be informed.

“The whole idea of the people who perpetrate these acts is to create fear, and more than fear, panic and hysteria,” he said.

“So when people are kept in the dark, they jump to all sorts of conclusions and they speculate, and that just encourages the very panic that the perpetrators are trying to create.”

He also pointed out that while the perpetrators appeared to be targeting Jews, the amount of explosives in the van posed an indiscriminate danger to anybody in its vicinity.

“Until we understand more about who is behind these incidents and particularly yesterday’s reported incident, we just don’t know what their motives are,” he said.

“We don’t know exactly where they’re coming from.”