UK police and emergency services are on scene after a passenger train derailed in southern England, authorities said Thursday.

The incident happened around 3:54 p.m. (10:54 a.m. ET) near Lewes railway station in East Sussex, around 45 miles south of London, according to British Transport Police.

“We’re responding alongside paramedics and the fire service and will provide more information as soon as we can,” BTP said on X.

Images posted to social media appear to show several train carriages on their sides, with people standing on top of them.

There are “no serious injuries or fatalities,” according to multiple British news outlets citing a source from the UK Department for Transport.

East Sussex Fire and Rescue Service said it was working with other emergency services at the scene and advised the public to avoid the area.

“We have ten fire engines, a Command Support Unit, technical rescue units, officers and other resources at the scene,” the fire service said in an update on Thursday evening. “We have been helping reach passengers and assisting other emergency services.”

UK Transport Secretary Heidi Alexander said she was “deeply concerned” by reports of the derailment and thanked emergency responders working at the scene to support those impacted.

“We are working quickly with the rail industry and local partners to assist passengers,” she added.

There was no immediate indication of the cause of the derailment. Some train services had been canceled and others were running at reduced speeds due to a heatwave – temperatures in some parts of southern England reached 35 degrees Celsius, or 95 degrees Fahrenheit on Thursday.

The UK’s Rail Accident Investigation Branch said it was deploying a team of investigators to the site of the derailment to begin gathering evidence.

Images circulating on social platforms shortly after the derailment showed overturned train carriages and emergency responders on scene. Laura Arnold

The TSSA transport union also expressed its concern over the derailment. “With a large number of passengers involved, their safety and wellbeing must come first. We thank all emergency services and rail staff responding at the scene and await to hear more,” it said in a statement.

Rail customers have been warned of “major disruption” for the next several hours, according to National Rail.

“No trains can run through Lewes and Haywards Heath until further notice. You will need to use an alternative route to reach your destination,” it said.

Train operator Southern Rail has advised the public not to travel with all lines through Lewes railway station shut down to allow emergency team, rail engineers and other specialist staff “to assess the situation and ensure the railway is safe.”

Thursday’s incident is the second serious train crash in the UK in two months. In June, two passenger trains collided in south-central England near the town of Bedford, killing one person and injuring dozens more.