Fire and Emergency said it received multiple calls about a large house fire on Wharenui Road in Riccarton, Christchurch after 1.30pm.
A spokesperson for Fire and Emergency said two fire engines were originally sent to the scene, but due to the number of calls they received, another two units were sent.
Windows on the two-story building were smashed with the insides of the home turned pitch black.
The white weatherboards of the home were charred black and orange around the garage, where firefighters were entering the property.
The spokesperson said four persons were accounted for from the home.
A passerby described the fire as "huge" and said the home appeared to be a student flat. Several young people could be seen standing outside the home and making phone calls.
Police were also in attendance after being notified of the fire at 1.35pm.
The cause of the fire is not yet known.
By Jaime Lyth