There was a track "irregularity" on the approach to the site of a train derailment near Lewes last week, an initial report has found - see a photo taken before the incident
The Rail Accident Investigation Branch has been investigating the derailment, which saw three carriages of a Southern Railway service from London Victoria flip on their side near Lewes
Around 150 people were on the train - one passenger told the BBC it felt like "we'd been lifted into the air", while another said when the train stopped they "were stood on the glass of the windows"
The report says there is evidence that "some movement" had previously taken place on the railway embankment, but there is no evidence of a significant slip
Thirty people were injured with 20 taken to hospital - two passengers who suffered serious but non-life threatening injuries remain in hospital
The railway between Lewes and Hayward Heath will be closed for at least one more week as the train is recovered and tracks are repaired
The report has also looked at the speed which the train driver was going at the time of the accident.
The RAIB said that the train was travelling at 65mph at the time of the accident, which is within the 70mph speed limit for the area.
Data also shows that the driver had applied the brakes at the point where the train derailed, and that the train had started to decelerate.
As a result of the train derailment, the initial report says that around 30 people were injured, 20 of whom required hospital treatment.
Some of them had "serious injuries", the report says. Authorities previously said two people had been left with serious but not life-threatening injuries.
"Significant damage was caused to the train and to railway infrastructure," the report adds.
The report says the accident took place "during a sustained period of hot and dry weather" - on the day, it was "hot and sunny, with little wind" and around 27C (ambient air temperature).
The embankment on which the railway runs is constructed of clay, sitting on alluvial/alluvium deposits, "consisting of loose clay, silt, sand and gravel", the report outlines.
These are sensitive to changes in water content and could move as moisture levels change, the report says.
The report says there is no evidence that a significant embankment slip occurred before the accident at this stage. However, there is evidence that some movement had previously taken place
The RAIB report also included CCTV images from a train, which it says appears to shows the irregularity in the train tracks which it says it has found.
In the image, taken from a train that passed through at 14:04 BST on the same day, it shows a irregularity "adjacent to the white ballast bags", according to the report.
Image source, Greater Thameslink Ralway / RAIBThe RAIB says an "irregularity" could be seen on the tracks over an hour before the derailment
The Rail Accident Investigation Branch has released its initial report into the incident, which took place at about 15:44 BST on Thursday, 13 August.
It says that a "track geometry irregularity" existed on the approach to the site where the train derailed "prior to the accident occurring".
Stay with us as we bring you more updates from the report as they become available.
The initial report from the investigation into Thursday's derailment in Lewes, East Sussex, has just been released by the Rail Accident Investigation Branch.
We are looking through it now and will bring you the key lines as we get them.
Katy Austin
Transport correspondent
We're anticipating an update today including some initial facts. It's still early stages in the overall investigation though - the final report won't come out for a while.
We know that experts from the Rail Accident Investigation Branch have been examining the accident site and the train itself, and taking a close look at the infrastructure.
Other evidence includes CCTV, data downloaded from the train, and signalling data.
Their job is to piece together what happened and come up with recommendations to stop something like this happening again.
Other investigations are done by the industry, and by the safety regulator the Office of Rail and Road.
Rachel Heath, who caught the affected train, told BBC Radio 4's Today programme she felt like "we'd been lifted into the air".
"Everyone was screaming and I just remember looking around and seeing so much panic and fear in people’s eyes, and all of a sudden it felt like we’d been lifted into the air and then came back down and the train just fell on to its side," she said.
Tracy McGregor was also travelling on the train, in carriage seven - one of the coaches which left the tracks.
She told the BBC: "When the carriage left the tracks, it felt like it went on forever.
"I took the brace position, I was preparing to die.
"When the train did stop, we were stood on the glass of the windows but the carriage was just full of earth."
She said the first emergency services arrived on the scene within 10 minutes.
Image source, Tracey McGregorTracey McGregor said when the train stopped, she was "stood on the glass of the windows" and the carriage was "full of earth"
Three carriages of a passenger left the tracks in Lewes, East Sussex, at around 15:44 BST on Thursday 13 August.
It happened as the 14:24 Eastbourne-bound Southern service approached the East Sussex town from London Victoria.
All lines between Lewes and Haywards Heath were closed following the derailment, with railway officials warning disruption will continue until at least August 26.
Image source, Jack Valpy/BBCAuthorities are investigating how a train derailed near Lewes in East Sussex
Good morning.
We are expecting an update today on the investigation into a train derailment where three carriages of a passenger train tumbled off the track in Lewes, East Sussex earlier this month.
Two people remain in hospital with serious but non life-threatening injuries and authorities said 18 others were also taken to hospital with less serious injuries.
They were later discharged.
A Rail Accident Investigation Branch team has been examining the derailed train and railway infrastructure at the site, in part reviewing CCTV footage and signalling data.
We expect to receive an update from investigators today. As always, our reporters are poised to bring you the key lines as they come in.
