This article was reproduced with the kind permission
of the British Broadcasting Corporation
14 November 2007, 14:59 GMT
The girl, thought to be aged six, was saved from the burning house in Coventry by neighbours using a ladder. Firefighters then rescued her mother.
The girl suffered burns to her upper body and legs.
The woman, in her 30s, was taken to a specialist burns unit in Nottingham. The man is being questioned.
The fire broke out shortly before midnight.
Neighbours of the woman and child later spoke about the night's events.
Pete McAndrews, 32, helped to look after the little girl after she was helped from the house in Langdale Avenue, Holbrooks. He said he heard the child crying and found her lying on the ground a few yards from the end-terraced property.
"She was quite badly burnt," he said.
"All her clothes were stuck to her and her hair was burnt.
"I grabbed her and took her out of there because things were falling out of the window and there was glass everywhere."
He said he remained with her until she was taken from treatment while his wife looked after her eight-year-old brother until relatives arrived.
The boy had got out through a back window, he added.
A spokeswoman for West Midlands Police said they were alerted to the fire by fire crews and that they were treating the incident as suspicious.
A spokesman for West Midlands Fire and Rescue said crews were called to the house in Langdale Avenue, Holbrooks, at 2345 GMT.
"Prior to the arrival of the fire service a girl was rescued by neighbours using a ladder at a rear bedroom window.
"Shortly after, a woman was rescued by firefighters," he said.
A West Midlands Ambulance Service spokesman said both the girl and woman suffered very serious injuries.
The girl has also been taken for specialist treatment at the Birmingham Children's Hospital.