Police are investigating a fire they say was deliberately lit in a car near Greymouth last night.
They say the fire quickly spread to a nearby house.
The occupants, including two children, managed to escape the Firth Street house unharmed.
Police want to hear from anyone who was near the house between 6pm and 6.20pm on Monday night.
Kate Hutchison posted on Facebook the car belonged her and she was at home with her children when the fire started.
She was organising an anti-child violence march and said all the signs for it were in the car and were destroyed in the fire.
Ms Hutchison's son, Leith, was killed in April last year.
A 30-year-old man, whose name is suppressed, has been charged with his murder.