A fire investigator has been called to a suspicious blaze in upper Riccarton overnight.

 A Fire and Emergency spokeswoman said they received the first call to the blaze on Fletcher Place at 1.15AM

 She said by the time fire appliances arrived the single story unit was well ablaze.

 Appliances from Wigram and Ilam stations attended the fire.

 All occupants of the social housing unit were accounted for.

 The unit has been completely destroyed.