Dozens of passengers were treated for breathing difficulties after a suspected chemical incident at London City Airport.
Two casualties were taken to hospital and 24 were treated at the scene, London Ambulance Service (LAS) said.
A spokesman for London Fire Brigade (LFB) said it was called to the airport at 4.11pm to "reports of a chemical incident".
No "elevated readings" were found and the terminal building was ventilated and searched.
The incident was "declared safe" by the brigade at around 7pm.
An LFB spokesman said: "Two complete sweeps of the airport building were carried out jointly by firefighters and police officers both wearing protective equipment."
LAS medics specially trained to treat people in hazardous situations also attended the scene.
Around 500 members of the public and airport staff were evacuated.
The closure of the airport led to travel chaos as all flights were suspended.
Several incoming planes from destinations such as Frankfurt, Amsterdam, Belfast City and Paris were diverted to other airports.