The fire at the remote house in Brone Park, Garvagh, was reported to police at 9am on Sunday morning but is believed to have started some time before.
The house owner, a lady in her 90s, was fortunately not at home when the fire started.
Local SDLP councillor Helena Dallat O’Driscoll said: “I would like to express my concern following a fire in the Brone Park area of rural Garvagh that has destroyed the property of an elderly woman.”
“Of course, I am very relieved that the owner of this property was not present at the time of the fire but my sympathies are with her as the loss of her property will no doubt be deeply distressing.
“The fact that the PSNI has now confirmed they are treating this as suspicious it is very worrying and will come as a shock to those in the local community.
“I would encourage anyone with information about this incident to come forward and assist the PSNI with their enquiries.
“I have also been in contact with the NI Fire and Rescue Service and would like to thank them for their response in dealing with the incident.”
A PSNI spokesperson said: “There were no reports of any injuries as a result of the fire which is being treated as suspicious at this time.”
Anyone with any information about this incident or who may be able to help with the investigation, is asked to call officers in Limavady on the non-emergency number 101 quoting reference number 683 30/01/22.”