Southland police believe a house fire, from which a father and his 2-year-old son managed to escape, was deliberately lit.
Emergency services were called to the blaze at a house in Seaward Rd, Edendale, shortly after 1am on Saturday.
Detective Chris Lucy said the house was well alight when they arrived.
"Luckily the occupant of the house and his two-year-old son, who were home at the time, were able to escape uninjured.
"The house has extensive damage and police are treating the fire as arson."
Police are appealing for any witnesses in the area at the time to contact Det Lucy on (03) 211-0400.
Information can also be passed on anonymously through Crimestoppers on 0800 555 111.
