South Yorkshire Police said they were still investigating the cause of the house fire which killed a two-year-old girl in Doncaster last night, who has been identified as Libby-Jayne Hornsby.
Investigators found that bedding in the main bedroom on the first floor was set ablaze but area manager Steve Green said there were no working smoke alarms.
"This was a truly tragic incident and our thoughts are very much with all of those affected," he said.
"Working smoke alarms give you the extra moments to escape if a fire starts and we once again urge people to have working alarms fitted on every level of their homes."
A neighbour called the alerted emergency services to the incident which was attended by two fire crews.