Seven people were killed and more than 50 were injured when a tram derailed in south London early Wednesday morning, according to police.
Investigators said the tram, which was going faster than permitted, was rounding a curve during a storm when it tipped onto its side.
Initially, British Transport Police said five people had died, but later that number was raised to seven.
The 42-year-old tram driver was arrested on suspicion of manslaughter.
It took emergency workers hours to free five people who were trapped when the two-carriage tram tipped over.
The Rail Accident Investigation Branch determined that the tram was traveling at approximately 12 mph when it went around the sharp curve.
"Initial indications suggest that the tram was traveling at a significantly higher speed than is permitted," the branch said in a statement.
I heard a massive crash at about 6:15 a.m., then heard shouting, then the emergency services arrived.
A train passenger described the moment the train derailed, saying, "everyone just literally went flying."
London's fire department said eight fire engines and four specialist rescue units were among the first responders.
This tram wreck was the first with onboard fatalities since the 1950s. Other data shows that 20 people were injured in 112 tram-related incidents since March of last year.
The Associated Press contributed to this report.
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