A woman was being questioned by the RUC last night after an arson attack in which a four year old boy was seriously injured.
Conor Lamont was snatched from his blazing bedroom by a neighbour before fire crews arrived to tackle the fire at Parkview, Castledawson, Co Derry.
The child is in a serious condition in the intensive care unit at Belfast's Royal Victoria Hospital with severe burns to his lungs, hands and face.
His mother, Ms Tracey Lamont, who was treated for shock after the blaze, was at his bedside today. She said: "I've been told his lungs are badly burned and his chest and hands. They are putting skin grafts on his right hand."
The blaze is believed to have been fuelled by petrol, although the cause has not yet been established.
A neighbour, Mr Martin Donnelly (29), who was hailed as a hero for rescuing the little boy, described the scene that met him inside the burning house.
"The front door of the house was wide open so I just went in. When I got to the bedroom I opened the door and I had to go back because the smoke was unbearable. I just got the child and got him out."
A local fire officer, Mr Stephen Todd, described Mr Donnelly as "quick and heroic
"If it hadn't been for him, the child would have had far more serious burns," he said.
The RUC said the attack was not sectarian and other motives were being investigated.
Police were also trying to establish a motive for a petrol bomb attack on a house in the Waterside area of Derry early yesterday, in which three young children and their parents escaped uninjured.
The device exploded in the kitchen, causing extensive damage. The attack was not believed to be sectarian.
Police and firefighters yesterday also rescued residents from flats in the Co Antrim seaside resort of Port rush after a fire was started deliberately.