Passengers were evacuated from Heathrow Airport on Monday evening following reports of a suspected hazardous substance.

Footage shows a group of travellers waiting outside Terminal 4 with their luggage as a precaution on September 8.

The check-in area was temporarily closed while authorities assessed the situation.

Following an inspection, no hazardous material was found, and the terminal was declared safe to reopen.

The Metropolitan Police said in a statement: 'Specialist officers attended the scene alongside the London Fire Brigade and London Ambulance Service and conducted a thorough search of the area.

'No trace of any adverse substance was found.'

Officials said that 21 people were assessed by the London Ambulance Service, with 20 treated and discharged at the scene and one taken to hospital.

Flight data shows that disruption to flights landing and departing from Terminal 4 was minimal during the evacuation.

The cause of the incident remains under investigation.

Heathrow Airport is London's main international airport and the largest in the UK. More than 67 million passengers travel through the airport annually on flights operated by around 90 airlines, flying to over 180 destinations in more than 90 countries.