Two adults and two children were taken to Newham Hospital after complaining about a chemical smell in their home in Barking Road, Upton Park, at around 1.20pm on October 28.
Manha Islam, who was just 14 months old, died while receiving treatment.
An inquest into her death was opened at East London Coroner’s Court, Walthamstow, on Thursday, November 13.
Senior coroner Graeme Irvine said: “The death was referred to me as it was strongly suspected that Manha’s death was as a result of exposure to a substance named aluminium phosphide.
“Aluminium phosphide is typically used as a pesticide or fumigant and is very hazardous.”
Mr Irvine said police investigated the chemical smell which seemed to be coming from neighbouring properties.
A 41-year-old man and a 26-year-old woman were both arrested on suspicion of manslaughter the following day.
The Met Police said the pair, who are not known to the victim, have since been released on bail.
The other child, aged six, and the two adults were also treated but their conditions were not life-threatening.
Whilst a post-mortem examination was carried out no clear cause of death was offered, Mr Irvine said, but the court awaits toxicological and histological examinations of samples.
The inquest was adjourned as the criminal investigation into her death continues.
