Hundreds of passengers were evacuated from one of the UK's busiest railway stations today as armed police headed to the scene following a suspected gas leak. 

British Transport Police officers were called to Farringdon in central London just after 9.40am this morning after a 'small number of passengers' reported feeling unwell.

Police were working at the station alongside London Ambulance Service and London Fire Brigade, and the wider area was evacuated while investigations continued. 

National Rail confirmed Farringdon was shut with no trains stopping and major disruption until at least 5pm while the emergency services deal with the incident.

Transport for London said the Elizabeth line was suspended between Paddington and Abbey Wood, with severe delays between Paddington, Reading and Heathrow.

Farringdon, Britain's eighth busiest station, is a key intersection in central London where the Elizabeth line, three Underground lines and Thameslink trains connect.

Thameslink confirmed no trains will run between London St Pancras International and Blackfriars, which are located north and south of Farringdon, 'until further notice'.

Ticket acceptance was organised with other operators, while the Metropolitan, Circle and Hammersmith and City lines were all running non-stop through Farringdon. 

A BTP spokesman said: 'Officers were called to Farringdon station at 9.42am today following reports of a suspected gas leak in the station, with a small number of passengers reporting feeling unwell.

'Officers are in attendance, alongside the ambulance service and the fire brigade, and the station has been evacuated while enquiries are conducted.'

A London Fire Brigade spokesman said: 'London Fire Brigade is currently responding to an incident at Farringdon station.

'Two fire engines, two fire rescue units and specialist officers are in attendance. The Brigade is working alongside partners at the scene. People are advised to avoid the area at this time.'

A London Ambulance Service spokesperson said: 'We were called at 9.40am today to reports of an incident at the junction of Farringdon Road and Clerkenwell Road, EC1M.

'We have sent resources to the scene including ambulance crews, an incident response officer, a paramedic in a fast response car, a clinical team manager and paramedics from our hazardous area response team.

'The incident is ongoing and we are working with our emergency services partners.'

And a Transport for London spokesperson said: 'The Elizabeth line was suspended to allow the emergency services to investigate a suspected gas leak at Farringdon station.' 

National Rail urged passengers to 'please check before you travel' after services were 'heavily impacted' by the closure and will take 'some time' to recover. 

The last gas leak impacting a London railway station was eight years ago when Charing Cross and Waterloo East stations were both shut in January 2018.

Some 1,450 people were evacuated and engineers located the gas escape at the junction of Craven Street with Corner House Street before making repairs.