The 27-year-old had been arrested on suspicion of child neglect following the fatal fire in Sutton.
A 27-year-old woman arrested as part of the investigation into a house fire which killed four young brothers has been released on bail.
Kyson and Bryson, aged four, and Leyton and Logan Hoath, aged three, were alone when the fire broke out at the terrace house in Collingwood Road, Sutton, on Thursday.
The woman, held on suspicion of child neglect, has been bailed until January.
It comes as flowers and other tributes continue to be left near the scene.
A local resident said there has been a steady stream of local people bringing flowers, teddy bears, balloons and notes.
“The atmosphere is quiet and respectful. People are kneeling and looking at the flowers and notes. Lots of children are bringing flowers too,” she said.
The road remains closed while forensic officers carry out their investigation into the cause of the fire.
Ch Supt Dave Stringer, borough commander for Croydon, Bromley and Sutton Police, confirmed nobody else was inside the property at the time of the blaze.
“We know it will have come as a great shock to the local community and as part of that community, we are here to offer whatever support we can,” he said.
The Met said formal identification of the boys is yet to take place.
Sutton United, whose football ground backs on to Collingwood Road, said it was deeply saddened to learn what had happened.
“The club’s thoughts are with the relatives of the children who sadly lost their lives, and with all those in the emergency services who attended the incident.”
It said it would observe a minute’s silence before their game against Harrogate, which is set to start at 15:00.