The search is part of an investigation into allegations of unreported stillborn children.

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, Biggaon Monday.

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

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

"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.

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

From the gate, two sheds, one in a state of disrepair, can be seen among the scrub.

Police confirmed on Wednesday that an excavator has been bought onto the site to continue the investigation.

Local residents say the property has been owned by a Christian sect called the Twelve Tribes for many years.

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 until the middle 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.

The Twelve Tribes is a registered religious organisation and runs cafes in the Blue Mountains and Picton.

The Picton cafe is called Common Ground.

The sect has been in operation in Australia since the 1990s with members numbering in the hundreds.

The Sydney Morning Herald penned an expose about the organisation in 2013, alleging that its members shun modern medicine.

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