A pensioner died and her sister was left critically ill after it is thought they used their gas cooker to keep warm.

Neighbours called police to the house in Hill View Road, Sunderland, yesterday, after becoming concerned that they had not seen the two women for some time

Officers forced their way in and were met with a strong smell of gas. The gas had come from the women's cooker, which was switched on, but not lit.

Inside, they found the two women. One was already dead, the second woman was taken Sunderland Royal Hospital.

Relatives are now being sought as police say they cannot be sure which of the sisters survived the tragedy.

Superintendent Jim Campbell, of Northumbria Police, said: "As to the cause of death and injuries we can only speculate. It could be suffocation, it could be carbon monoxide, it could have been due to hypothermia. I am told the house was filled with gas."

Alan Campbell, of Age Concern, said: "We strongly advise older people not to use open cooker rings to keep warm in winter.

"We urge people to get in touch and we will do all we can to help," he said.

A post mortem examination will be carried out.

Anyone with information call 0191-454 7555, ext 66243.