A man has been charged over the discovery of what police have described as a commercial-grade clandestine illicit drug laboratory in Canberra's south.
Part of the industrial suburb of Hume was placed in lockdown on Tuesday night while police investigated the lab.
Stanley Hou, 35, from Lyneham appeared briefly in court charged with manufacturing a large quantity of controlled precursors, for the manufacture and sale of drugs.
Hou did not apply for bail, and will reappear in court on Monday.
ACT Chief Police Officer Rudi Lammers said the lab was part of a major operation.
"I would imagine the street value would be many, many millions of dollars," he told 666 ABC Canberra.
Officers allegedly uncovered the drug laboratory after entering a building on Sheppard Street about 2:00pm (AEST) on Tuesday.
It followed an investigation by police and WorkSafe ACT after workers in the area were overcome by fumes in February.
ACT Work Safety commissioner Mark McCabe said the source of those fumes could not be identified initially, and an investigation had continued over the past couple of months.
"That investigation culminated in the identification of a property that was visited by WorkSafe ACT inspectors and members of the AFP," Mr McCabe said.
Police allege a large quantity of chemicals commonly used for making ecstasy was also found in the building.
"There were two and a half tonnes of chemicals that could be used to produce drugs," Assistant Commissioner Lammers said.
Neighbouring businesses in the industrial estate were evacuated as a precautionary measure.
"We know from previous experience just how volatile and dangerous it can be," Assistant Commissioner Lammers said.
The Monaro Highway and surrounding roads were closed for a period causing significant traffic delays.
Sheppard Street and the Monaro Highway have since reopened.