Vomiting residents were rushed to hospital sparking fears of a chemical incident in south London.
Emergency services were scrambled to Alwold Crescent in Lee amid fears locals may have suffered an allergic reaction on Sunday.
Witnesses said several people suffered a reaction to an unknown substance.
Taxi driver Ian Crouch, 39, told the Sun that emergency services appeared to be investigating the sewage system.
Five fire engines, paramedics and police were all deployed to deal with the incident.
A spokesman for the Metropolitan Police said the incident was not believed to be crime-related and the investigation is being led by the London Fire Brigade (LFB).
A spokeswoman for LFB added: "There was a smell of an unknown chemical at an address in the area and we are investigating that. Some people have been removed as a precaution.
"Some people have been taken to hospital also as a precaution."