A woman and two children have been killed at a house in Rotorua overnight.

Police said they arrived shortly before 10.30pm on Monday at the property on High St in Glenholme, where they found two dead children and a woman with life-threatening injuries.

"Despite extensive efforts by police and ambulance crews, the woman died at the scene," Bay of Plenty acting district commander Inspector Logan Marsh said.

A man at the address was assisting police with inquiries, and no-one else was being sought at this time.

"This was an incredibly traumatic incident for all those involved. Our focus now is on supporting the family, our first responders and getting answers to what occurred last night," Marsh said.

"We know this event will be felt widely in the community and people will want answers. We are methodically working through the scene, including a detailed forensic examination."

He said this could take several days and there would be a police presence in the area.

"We know people will be understandably shaken following this incident and police will be carrying out additional reassurance patrols over the coming days and nights in Glenholme and the wider community.

"Out of respect for the victims and their family, we ask that people refrain from speculation or conjecture. Our focus remains on establishing exactly what occurred and providing answers for those affected."