South Wales Police has concluded its investigation into the explosion at a property in Seven Sisters on June 24.
The cause of the explosion has not been deemed suspicious and the most likely explanation is a combination of ageing LPG gas equipment and environmental conditions.
Detective Inspector Gareth Eynon said: “This was a tragic incident and our thoughts remain with the family.
“The police investigation has now concluded there was no criminal cause of the explosion.
“We would like to again thank the community for their support during our investigation.”
The woman injured remains in a critical but stable condition, the two children are in serious but stable conditions.