The blast in the Staffordshire commuter village of Cheddleton, near Leek, ripped off the roof of the house shortly before midnight on Thursday and started a fierce fire.
Neighbours tried to enter the house after hearing screams but were beaten back by 15ft flames.
Inside the house were Roderick Hine, 44, and three of his partner's children, aged 16, 10 and seven. Their mother, Amanda Carter, 35, had recently moved to the house to live with Mr Hine after separating from her husband. She was working a night shift at a nursing home in Cheddleton when the explosion happened. Her husband, Mark Carter, who was at the former marital home with the fourth of their children, was said to be in deep shock and mourning.
Staffordshire Police were investigating reports of a man running away from the scene, and their inquiries may also draw on CCTV images from a security camera at the house next door to Mr Hine's home.
Officers arrested a man in his thirties shortly after 9am yesterday. He was believed to be a former boyfriend of Samantha, the eldest of the children.
The unstable state of the house prevented police from removing the bodies of the victims for much of yesterday, but officers managed to gain access by the evening and the bodies to were taken to a mortuary for post-mortem examination today.
Mr Hine and the children Samantha, 16, Trisha, 10, and Marcus, seven were known and liked in the village, where the younger children were involved in Beavers and Brownies.
Mr Hine worked at a local agricultural firm, Bateman's, where his brother, Rob, is a director. He had developed a strong relationship with Marcus, the youngest of the children, according to a family friend, Heather Johnson.
"The little boy was with Rod all the time," Mrs Johnson said. "He liked bikes, they both liked bikes and you used to see the little boy with Rod while he was fixing his bike. Rod was a wonderful person. I am so devastated. Everyone in Cheddleton is devastated."
Local education authority counsellors were helping children cope with tragedy at Beresford First Memorial School, attended by Marcus, Churnet View Middle School, where Patricia was a pupil, and Leek High School, which Samantha attended.
"They were making a new life for themselves and now that life has been wiped out," said one of Mr Hine's colleagues, John Harvey.
He described being woken in the night by sirens and said he was unable to get close to the house because of the flames. "I ran down to the house in just my T-shirt and was asking the paramedics if the children were still inside," said Mr Harvey. "I spoke to a neighbour who said he had tried to smash a window and could hear children screaming."
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