Neighbours photographed a gas team at work in a street just eight days before a house blast left a girl of four dead and three others hurt.
Worried residents claimed they could smell gas at least two weeks prior to the tragedy and said the gas company had been warned they feared a leak.
Many said they had experienced headaches, dizziness and difficulty with their breathing.
The terrace house collapsed just after 7am on Monday.
The victim was named locally as little Sahara Salman.
Her family had apparently been in touch with the gas company for a week before the explosion.
Friend Thoheed Maricar, 52, said: “The mum was saying ‘my third child is missing’ but she couldn’t really talk. She was crying and screaming.
“The girl is a beautiful, cute four-year-old. She was a happy girl. She played around a lot and was very active.”
Her parents as well as two of her siblings were said not to be seriously injured in the blast in Thornton Heath, South London.
Resident Amarjit Kaur shared images of engineers working on the street in photographs dated July 31, but said she had not seen them since. A neighbour who lives opposite the incident, Delroy Simms, 62, said he could smell gas for “at least two weeks” before the blast, saying the situation was “a time bomb”.
Mr Simms, who has been evacuated to a hotel, was hailed as a hero alongside Kutoya Kukanda, 50, after they rescued three children from the rubble.
He said he was with his neighbour when she alerted the gas company on Wednesday, five days before the blast. He said: “She was telling them, ‘the smell, it’s really strong, someone needs to be here’.
“I was there during the conversation. The council knew about these calls too.”
Labour MP for Mitch-am and Morden, Siobhan McDonagh, said she has written to gas firm SGN demanding answers. She said: “This should never have happened, we will get to the bottom of it.”
On Monday a spokeswoman for SGN, which is the gas emergency service in the area, said: “Our deepest sympathies are with the family of the child who has tragically died as well as those injured.
“We’d like to reassure everyone our engineers are working closely with the emergency services. Given the ongoing police investigation, it is inappropriate to comment any further at this stage.”