A caravan laden with explosives that was potentially going to be used to target Jewish sites has been linked to a man already in custody after investigations into a spate of anti-Semitic attacks.

The van was found abandoned on a semi-rural road in Sydney’s northwest outskirts and reported to authorities, sparking a massive, multi-agency probe that includes counter-terrorism investigators.

Police on Thursday revealed the owner of the caravan, the presence of which was reported to authorities on January 20, was already in custody on unrelated charges laid by a strike force set up to find those responsible for escalating anti-Semitic incidents in Sydney.

No detonator was found in the van alongside the explosives, but Premier Chris Minns described the find as a “potential terrorist event”.

Details of the discovery were only made public on Wednesday afternoon – nine days after police found the explosives – when media reported information about the investigation.

NSW Police Deputy Commissioner David Hudson said the caravan’s owner was already in custody on “peripheral charges” at the time the discovery was made.

Search warrants executed as part of that previous investigation, carried out by investigators from a specialist police task force, revealed evidence of further offences, he said.

Robert, the owner of the Dural property near where the caravan was parked, said he had driven past the vehicle a number of times and thought nothing of it.

“I’ve passed it two or three times … I didn’t know why it was sitting there,” he said.

“Someone pulls up outside your house with some explosives – would you be frightened?”

Mr Minns and police defended the delay in going public with details of the find, a decision criticised by Jewish leaders for leading to further fear within the community.

The investigation had already been “significantly compromised” by the media leaks, forcing a rethink of investigators’ strategies, Mr Hudson said.

Authorities would also not be drawn on any potential links between the caravan find and the influence of foreign actors, who federal investigators have said could be behind some of the recent anti-Semitic attacks in Australia.

“I’m not going to speculate on that,” Mr Minns said, although he lashed out at the “appalling bastards” behind the crimes.

“Bad morals, bad ethics and bad people will commit these crimes,” he said.

The explosives were sourced from a mine and investigators were liaising with the manufacturers to trace more information, police said.

Prime Minister Anthony Albanese joined the chorus of politicians to condemn those behind the potential anti-Semitic bomb plot and didn’t quibble with Mr Minns’ description of the incident being a possible act of terrorism.

“It’s clearly designed to harm people, but it’s also designed to create fear in the community and that is the very definition,” he said.

Israel’s ambassador to Australia Amir Maimon said he was deeply alarmed over the foiled potential attack, although he added he had been assured that every measure was being taken to protect the community.

NSW police are also investigating three separate anti-Semitic graffiti incidents in Sydney overnight, including the apparent targeting of Mount Sinai College, a Jewish primary school in the city’s east.

They follow a spate of recent attacks, including the arson of a childcare centre near a synagogue, the targeting of a Jewish community leader’s former home and the spray-painting of anti-Semitic slurs in various prominent locations.

At least 10 people have already been charged over those incidents.