Assistant Commissioner Holland has finished his press conference in Coonabarabran on the deaths of a 6yo and 7yo in north-west NSW.

"It's a confronting tragedy that shouldn't have occurred," the assistant commissioner said.

"We've got two young kids who obviously have been looked after by their maternal grandmother in a small country town.

"The town needs to band together now and understand that this has happened."

The grandmother was "known to police but not adversely", the assistant commissioner said.

Her mental health history is "being investigated", he said.

Assistant Commissioner Holland was asked how the family was doing.

"Not well, it's probably the best way to put it," he said.

"Anyone confronted with the death of one child, let alone two in these circumstances, would be struggling."

Police believe that the grandmother and two young children moved to the area 11 months ago. 

"Something like this affects a community in a very, very hard way," Assistant Commissioner Holland said.

"A death in a small community has an impact on the whole community.

"The death of two, young, innocent boys has a major impact."

Assistant Commissioner Holland said the woman was the sole carer and the boys had "been in her care for some time".

She is understood to be the boys' grandmother.

"Biological parents have been informed," he said. 

Police faced a "confronting situation" and had to "force entry to the house" when they responded yesterday, the assistant commissioner said.

The woman had "attempted self harm" and was immediately placed under arrest.

The two boys were found in separate rooms, she said.

A 66yo woman who was taken into custody on Monday remains in hospital, Assistant Commissioner Holland said. 

She will be detained for "the near future" and upon release, will be "handed back to police custody", he said.

She will "likely face serious charges". 

Assistant Commissioner Holland says that forensic examination of the house is underway.

"Confirmed cause of death ... at this stage has not been identified," he said.

Police are also taking statements from witnesses and people who live in town. 

Police are about to give an update on the investigation into the deaths of two children in north-west NSW on Monday. 

The boys, aged 6 and 7, were found dead inside a home in Coonabarabran after a "concern for welfare" report. 

The town is about 150km north-east of Dubbo with a population of more than 2,000. 

We can expect to hear from Assistant Commissioner Andrew Holland, the NSW Police Western Region Commander.