A passenger train derailed in eastern England on Friday less than 24 hours after three carriages of another train overturned in the southeast severely injuring two people.
The UK government's Department for Transport said no passengers were injured in the latest derailment near Wickford in Essex.
On Thursday, a commuter train carrying 150 people between London and England's south coast veered off the tracks near the town of Lewes.
Two people suffered severe injuries, while 18 others were treated for less serious injuries, police said Friday.
Train accidents, particularly fatal ones, are relatively rare in Britain.
The Rail Accident Investigation Branch (RAIB) was probing the two derailments, which came amid exceptionally hot weather.
"I appreciate the public will be concerned at the news of two derailments of passenger trains over a short period of time," Martin Frobisher, of Network Rail, which operates rail tracks in Britain, said.
"I want to reassure them that Britain's railways still rank among the safest in the world, and that safety is always our first consideration on the railway."
Frobisher noted "the unprecedented hot and dry weather that we have experienced this summer has presented exceptional challenges to the railway" but urged people to avoid speculating on the cause of any incidents.
He vowed RAIB and Network Rail probes into the derailments "will look at all possible causes and factors".