Published Thursday, 04 September 2014
The scene of the fire at Carryduff in Co Down. (© UTV)
Police said on Thursday that, due to receiving new information, they are now treating the fire as suspected arson.
It was initially being treated as not suspicious.
The woman, aged 57, was detained at a police station in north Down on Wednesday and remains in custody assisting police with their enquiries.
Samuel Carson, 91, died after a fire at an adjoining property spread to his home in the Co Down town in the early hours of Tuesday.
The blaze broke out at a garage and oil tank at Thorndale Park, before spreading to Mr Carson's oil tank and house on Hillsborough Road.
Emergency services were called to the scene at 1am and it took 40 firefighters four hours to battle the blaze.
A Northern Ireland Fire & Rescue Service (NIFRS) Spokesperson said: "Firefighters rescued a 91-year-old man from the property and alongside ambulance personnel they carried out CPR but sadly the man died at the scene.
"Fire crews dealt with the fire involving the bungalow, the garage and the oil tanks by 5am. In total seven fire appliances and a command support unit and around 40 firefighters attended the incident."
It is understood that Mr Carson lived alone.
© UTV News