A 26-year-old man has been arrested following a fire at a property in Tonypandy, which left one woman in a "critical" condition and three children needing medical attention.
The fire broke out at a house on Tyntyla Road on Tuesday 21 September. Emergency services were called out to the address at around 4:45pm.
A 28-year-old woman, who was trapped inside, had to be extracted from the premises by fire and rescue officers and taken to Morriston Hospital.
The man police have arrested in connection with the offence remains in police custody.
Neighbour Elwydd Jeffrey said: "I have never seen such black smoke. It was so thick and dense you could hardly see through the window."I thought there would be no house left, that's how bad it was."Three children had to be treated for smoke inhalation following the blaze.
Police are currently investigating to establish the circumstances surrounding the incident.Detective Chief Inspector Sarah Lewis said: "We are keeping an open mind as to what caused the fire and at this stage we cannot rule anything out."We have a team of officers who are working hard to establish what happened."Anybody with relevant information is asked to contact South Wales Police.