A resident cleaning their home sparked a full chemical alert that led to neighbours being evacuated from nearby properties in east London.
Police, specialist hazardous response units, paramedics and fire crews responded to concerns about a strong smell of chemicals coming from the address in Woodman Road, Chigwell about 5.40pm on Sunday.
One eyewitness saw up to 20 emergency vehicles in the street near Hainault Health Centre.
Scotland Yard said: “A number of addresses were evacuated as a precaution. There were no reports of any injuries.
“The incident was not treated as suspicious. Someone was cleaning their house.”
London Fire Brigade said one woman was treated on scene by London Ambulance Service crews.
Two fire engines from Woodford and Romford stations and three fire rescue units from Bethnal Green and Euston attended.
A 25-metre cordon was put in place as a precaution for around four hours.
An LFB spokesman said: “Firefighters were called to a suspected chemical incident at a flat on Woodman Road in Chigwell yesterday.
“Crews investigated a strong smell of chemicals in the property and used detection, identification and monitoring equipment to sweep the building, but no elevated readings of chemical substances were found.
“The Brigade was called at 5.50pm and the incident was over for firefighters by 9.43pm.”