While its members often keep to themselves the organisation has been accused of physical punishment of children and discouraging its followers from accessing medical help.

But who are they?

The registered Christian organisation has been in Australia since the early 1990s.

However it was originally founded in the United States in 1973 by a former high school guidance counsellor and carnival showman named Eugene Spriggs.

The sect works to serve Master Yahshua, which is the Hebrew name for Jesus and is often likened to Amish communities.

Members of the Twelve Tribes run businesses and farm large parcels of land in Picton, the Blue Mountains and Bigga, NSW.

Their Picton community is located along Remembrance Driveway (Old Hume Highway) and is known as Peppercorn Creek Farm.

The Twelve Tribes' website describe the 'little farm' as an idyllic location for families.

"We have 22 acres in a valley of the Razorback Range, with a beautiful creek winding through it, and peppercorn trees dotted along the water's edge...hence the name Peppercorn Creek Farm," the description reads.

"Eight families, along with a number of single men and women, live here.

"We have many children so our life is busy caring for them.

"We teach them at home, and always have our young ones by our sides helping us with all the many daily living needs.

"They enjoy being involved in what we do and building up our life.

"They know they're necessary."

The Picton tribe also runs popular cafe, Common Ground, located just down the road from Peppercorn Creek Farm.

In the Blue Mountains, the tribe runs the Yellow Deli in Katoomba - which was also formally known as Common Ground.

The restaurants serve a range of signature sandwiches and a range of teas.

However, the sect has been plagued with allegations of physical punishment of children throughout the past few years.

Back in 2013, former Twelve Tribes members Mark and Rosemary Ilich revealed to the Sydney Morning Herald what life was like inside the sect.

They first visited the organisation at Peppercorn Creek Farm and said they "were sold".

The couple said they handed over all of their possessions and the discipline of their children to the Twelve Tribes.

"It's called 'the rod and reproof', " Mr Illich told the Herald.

"The kids are not meant to cry. They're meant to 'receive' their discipline quietly.

"Then you tell them why you hit them and they say, 'I'm sorry, I'm sorry.' It becomes a ritual."

The Sydney Morning Herald expose also alleged that Twelve Tribes members shun modern medicine.

A former leader of the sect told A Current Affair in a report from earlier this year that "members were discouraged from seeking outside medical help, even in cases of serious illness".

The NSW Police Force commenced its first investigation into the Twelve Tribes on Monday after allegations of unreported stillborn children recently arose.

Under the Birth, Deaths and Marriages Registration Act 1995, it is illegal not to report the births of stillborn children.

The Service NSW website states that 'stillbirths are legally required to be registered as births, and will contain a notation of the stillbirth'.

Officers from the Blue Mountains Police Area Command executed search warrants at Peppercorn Creek Farm on Remembrance Driveway (Old Hume Highway) and a property on Bigga Road, Bigga on Monday.

A NSW Police media spokeswoman confirmed that the planned police operation would continue at both properties.

"Detectives from Blue Mountains Police Area Command are executing a crime scene warrant," she told the Advertiser.

"Investigations are ongoing under strike force Nanegai

"No arrests have been made and no further information is available at this stage."

Police worked through the night on under lights at the rural Bigga Road property on Monday and have since brought excavators onto the site.

The property is surrounded by thick bush, which covers the area where police are working back from the main road.

The investigation is being led by detectives from Blue Mountains Police Area Command with Hume Police District's police rescue unit and officers supporting.

Police expect the investigation to continue to the end of the week.

The spokeswoman said police were expected to provide an update once the investigation had concluded.

This investigation follows a search warrant that was executed at the Peppercorn Creek Farm property on February 19.