The Transport Secretary said rail safety remains an “absolute priority” following incidents at Lewes, East Sussex, on Thursday and Wickford, Essex, on Friday.
Both derailments are being investigated by the Rail Accident Investigation Branch (RAIB), with their causes yet to be established.
The incidents happened during a period of exceptionally hot weather, but Ms Alexander warned against speculation over whether the conditions played a role.
She said:
“I am thinking of those who were affected by the derailment in Lewes yesterday, as well as those involved in today’s derailment in Wickford.
Heidi Alexander in front of the newly branded Great British Railways carriages
“The Rail Accident Investigation Branch has been deployed to both sites and is expected to report on the causes in due course. It is important that we do not speculate in the meantime.
“I understand passengers may be concerned about news of two incidents on the network, but the industry has been taking proactive steps to manage the heat for example by closely monitoring track temperatures and putting speed restrictions in place where needed.
“This afternoon, I spoke with Network Rail and other industry partners, including those on the scene at Lewes, to seek assurances that everything possible is being done to avoid similar incidents occurring.
“Our rail network is amongst the safest in the world and while incidents like this are thankfully extremely rare, when they do occur, they are taken very seriously.
“Safety is our absolute priority. The industry will ensure that all lessons are learnt and I continue to be briefed on the operational response.”
The first incident involved a Southern passenger service travelling from London Victoria towards Eastbourne near Lewes on Thursday afternoon.
Around 150 people were reported to have been on board. Three carriages overturned, with two passengers suffering severe injuries and another 18 sustaining minor injuries, according to subsequent reports.
A second derailment happened at around 2.12pm on Friday, involving a Greater Anglia passenger train south of Wickford station.
British Transport Police said the rear carriages derailed but remained upright. Emergency services attended and no injuries were reported.
Network Rail said the hot weather was presenting “exceptional challenges” for the railway, with track temperatures being monitored and speed restrictions imposed where required.
Heidi Alexander in Japan
Steel rails expand as temperatures rise and can distort or buckle in extreme conditions. However, there is currently no confirmed link between the weather and either derailment.
The incidents have particular significance locally because Ms Alexander represents Swindon South alongside her Cabinet role as Secretary of State for Transport.
She has held the transport brief since November 2024 and has overall responsibility for the Department for Transport.
The derailments also come amid significant changes to Britain’s railways, including the Government’s programme of bringing passenger services into public ownership.
Southern transferred into public ownership at the end of May, while Greater Anglia had previously made the same transition.
The Government is also progressing plans to bring track and train operations together under Great British Railways.
The RAIB investigations are expected to establish the circumstances and causes of both derailments and make any safety recommendations considered necessary.
