Authorities are searching for the origin of a mysterious white substance found at a mosque in Perth.

Officers quickly rushed to the place of worship on William Street in Northbridge at about 1am on Saturday after reports of a melee outside the building.

When officers arrived at the scene, they found a white, ‘non-suspicious substance’ on the steps outside, 7News reports.

WA Police Commissioner Col Blanch said the powder posed no risk to the community.

However, he added that the discovery had been concerning.

‘We don’t know if it was in fact targeted at the mosque, but certainly, given the location, we are doing an investigation,’ he said. 

The matter has been elevated to the State Security Investigation Unit, which handles serious security threats such as suspected terrorism and extremism.

CCTV footage will be reviewed by police as they hunt the person who may have placed the substance in the area. 

Any connection between the scuffle and the powder is also being investigated.

Police found a white substance outside a mosque on William Street in Northbridge, Perth, about 1am on Saturday 

WA Police Commissioner Col Blanch said the powder had never posed any risk to the public but that its placement had been concerning

It is unknown whether the white substance was an attempt at intimidation, a prank or unrelated to an alleged terror plot.

Perth had already been on high alert as, just hours before, it was revealed Jayson Joseph Michaels, 20, had been charged in an unrelated incident.

He was accused of preparing for a ‘terrorist act’ on public buildings, including mosques.

Police said they had carried out a search at a home in Bindoon, about 80km from Perth, where officers allegedly seized firearms, imitation firearms, a knife collection, ballistic vest, gas masks, and lock-picking equipment.

Commissioner Blanch told reporters on Friday that officers allegedly also found a notebook written as a ‘manifesto-style document’.

It ‘outlined preparations for a terrorist attack at significant locations, including the WA Police Headquarters, Parliament House and places of Muslim faith’, he said.

He alleged the messages contained ‘white supremacy ideology’ and ‘anti-Muslim ideology’, ‘antisemitism’ and other conversations about minority groups, which he described as ‘abhorrent’.

Following the raid on the Wheatbelt property, Michaels, who lives with his parents, was charged with five offences.

Premier Roger Cook said the young man’s alleged plan had been for a ‘mass casualty event’.

He said the counter terrorism team ‘had prevented an alleged act of terror in our city’ to ‘attack the heart of our democracy’.

‘Whatever our differences, we all have the right to go about our lives free from the fear of violence,’ he said.

After an appearance at Perth Magistrate’s Court on Friday, Michaels’ bail was refused while the matter remains before the court.