A Greater Anglia train has partially derailed near Wickford in Essex.
An image taken at the scene shows the train to have come off the tracks, but it remains upright.
British Transport Police confirmed that paramedics and fire crews are on the scene after the incident at 2.12pm.
They said that the ‘rear carriages’ derailed, but there are currently no reported injuries.
As the situation develops, a ‘do not travel’ warning is issued between Shenfield and Southend Victoria until further notice.
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An initial statement from National Rail said: ‘There is a problem currently under investigation between Southend Victoria and Wickford, meaning that all lines are blocked.
‘As a result, trains running between Southend Victoria and London Liverpool Street will be cancelled.’
‘Major’ disruption, delays, and cancellations are expected until at least 6pm.
A spokesperson later confirmed that responders were ‘working quickly to understand the situation and to provide assistance where needed’.
‘We will provide further information in due course.’
Inspectors from the Rail Accident Investigation Branch (RAIB) have also been sent to Wickford to ‘begin gathering evidence’.
It comes not even 24 hours after a Southern Rail train derailed near Lewes railway station in East Sussex, leaving two severely injured and another 18 with less serious injuries.
The two passengers remain in hospital, while the others have been discharged. Fortunately, no injuries sustained were ‘life-threatening’.
With around 150 passengers on board the service from London Victoria to Eastbourne, people were trapped for hours after several carriages turned on their side, prompting a major incident to be declared.
Speaking in the aftermath, passengers recalled how the train began ‘rocking’ before ‘everything got thrown forward’.
One told BBC News that it ‘skidded for quite a while’ and, upon turning around, he noticed the back of the train was smoking.
People were seen with bloody wounds and head injuries.
Another described how ‘everything went topsy-turvy’, leaving her ‘pretty banged up’ as a result.
Again, the RAIB ‘deployed a team’ to the site, with a probe now underway to determine the cause of the derailment.
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