Warwickshire Police have issued an update on their investigation and the situation of those injured following Thursday's house fire in Rugby.
The fire broke out shortly before 3am on Thursday, November 15, in Wentworth Road, Rugby.
One woman and three children suffered serious injuries and were taken to hospital.
Detective Inspector Paul Thompson from Warwickshire Police Major Investigation Unit said: "Investigations are ongoing following a fire in Wentworth Road, Rugby, in the early hours of yesterday morning. Following joint enquiries with the fire service yesterday we can confirm the fire is being treated as arson.
"A five-year-old boy injured in the fire remains in a critical but stable condition in hospital. A woman and two other children continue to be treated in hospital for burns and smoke inhalation.
"A 21-year-old man from Rugby arrested on suspicion of arson with intent to endanger life remains in police custody and will be interviewed by officers today.
"Enquiries are ongoing and it is important anyone with information, no matter how insignificant it may seem, contacts police."
"Officers will remain in the area throughout the day as inquiries continue and to provide reassurance to the local community. If anyone has any information or concerns please talk to one of them."
Police and fire spoke at the scene on Thursday afternoon saying the property was completely damaged by smoke, and the ground floor destroyed by fire.
Anyone with information can call 101 quoting incident 29 of 15 November 2018. Alternatively, information can be provided anonymously to the independent charity Crimestoppers on 0800 555 111.