A father and son are accused of deliberately torching two drug labs in remote bushland, sparking a fire that burned 50 hectares in the Blue Mountains and could have threatened homes.
It's believed the clandestine labs had been operating for some years in a sophisticated operation that was supplying millions of dollars of the drug ice to the streets.
The men, aged 55 and 27, were arrested on Sunday night and have been charged with the large commercial manufacture of a prohibited drug and contaminating a water catchment area.
The son has also been charged with lighting the fire and letting it escape on to public land.
Acting Assistant Commissioner Peter Cotter told reporters on Monday that police had been monitoring the operation from last month and were about to raid the bushland labs when high fire danger conditions aborted the plan.
On Wednesday, the bushfire broke out, destroying the two labs hidden in the Blue Mountains National Park and burning through about 50 hectares before Rural Fire Service and national park crews brought it under control.
Mr Cotter said police did not think the drug lab operators were tipped off about the police operation.
"There's a chance they became aware of our presence somehow ... and that spooked them."
The father and son, from West Hoxton in Sydney's west, have been refused bail and are to appear in Sutherland Local Court on Monday.
Mr Cotter said police were talking to other people in relation to the drug labs.
He said police had no information that linked the operation to any outlaw motorcycle gang or other organised crime group.
However, he said police had "strong suspicions" that other people had been involved for a long time.
Mr Cotter said the pair had been "relatively silent" during police questioning so far.
He said the labs were about 250 metres apart and only accessible on foot, in remote bush, about 60km west of Camden.
There was a mix of makeshift sheds and tarpaulin-covered areas, camouflaged with vegetation, making them hard to spot from the air.
The bushfire was finally extinguished on Sunday night after dozens of firefighters and six aircraft crews worked to bring it under control.
Mr Cotter said lighting a fire at any time was dangerous but lighting one in the past week's high fire danger conditions could have been "catastrophic" and could have threatened many homes on the edge of the national park.
He said the fires destroyed valuable evidence at the drug labs but previous covert inspections and forensic work at the scene meant police still had plenty of material to build a case.