Emergency services responded to a family harm incident on Henderson Ave, Flaxmere at 11.10pm on Saturday.
A police spokeswoman said one person had been arrested and was in custody after one person suffered serious injuries.
A Hawke's Bay District Health Board spokeswoman confirmed a female in her late 40s was in a critical condition, last night in intensive care at the Hawke's Bay Hospital.
Meanwhile, emergency services were called to a "well-involved" fire on Ramsey Cres, Flaxmere at 4.55am today.
Fire communications shift manager David Meikle said four appliances; two from Hastings and two from Napier attended the blaze.