A 66-year-old grandmother is expected to “face serious charges” over the death of two young boys inside a home in country NSW, with police treating the incident as an alleged double murder.

The children, aged six and seven, were found by police, who forced their way into a property on Emu Lane in Coonabarabran during a welfare check just after 2pm on Monday.

The boys’ maternal grandmother and sole carer was taken into custody at the home and has been transferred to a mental health facility in Orange “where she will be detained for the near future until she improves”.

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“Upon release she will then be handed back to police custody where it is likely she will face serious charges,” Assistant Commissioner Andrew Holland said on Tuesday.

He confirmed police are treating the incident as an alleged double murder.

Holland said officers were met with a “confronting” situation, with the boys discovered in separate rooms and the grandmother found with self-inflicted injuries.

“She spoke to police about what had taken place and what had occurred in the house at that time,” he said.

“That information is being included in the investigative process.”

Police said the boys had been in the grandmother’s care “for some time” and had moved to Coonabarabran about 11 months ago.

The children’s biological parents have been informed of the tragic news.

“Anyone confronted with the death of one child let alone two in these set of circumstances will be struggling,” Holland said.

A forensic examination of the home will not be finished until Wednesday and detectives are still taking statements from witnesses and people around town who knew the family.

“At this point, the post-mortem for the two young boys is scheduled for Thursday morning,” Holland said.

“That will give us a confirmed cause of death which at this stage has not been identified as yet.”

Police said they were tipped off by a call to the Department of Communities and Justice, with an alert then sent to triple-0.

Holland said further information was passed on “and that’s why police forced entry to the premises”.

The grandmother is known to police, “but not adversely”, Holland said.

‘Terrible tragedy’

Coonabarabran is a town of about 3500 people and is a six hour drive northwest of Sydney.

Holland said the death of two children is “incomprehensible” and would shock the country community.

“Something like this affects our community in a very, very hard way,” Holland said.

NSW Police Commissioner Karen Webb described the incident as a “terrible, terrible tragedy”.

“The NSW Police will support the town of Coonabarabran in this horrific time,” Webb said.

“Every resource will be made available for both local police who responded to the call for help, and for the distraught family and community.”