The tram's data recorder showed it was moving at 43.5 miles per hour as it entered a curve in the track where the speed limit was 12.5 miles per hour, a preliminary report from the Rail Accident Investigation Branch
After the tram derailed on November 9, it skidded along on its right side for about 25 meters (27 yards) before coming to a halt, it said. The right side of the tram was "severely damaged" where it was in contact with the ground.
Besides the seven passengers who lost their lives, 51 people needed hospital treatment after the crash, with eight of them suffering injuries described by the London Ambulance Service as serious or life-threatening.
The RAIB report said about 60 people were believed to have been on the tram.
Driver arrested over crash
The tram's driver, a 42-year-old man, was released on police bail Thursday after being arrested following the crash on suspicion of manslaughter. He has not been named by the British Transport Police.
He was the only member of staff on board the tram, which crashed soon after 6 a.m. on a dark and rainy morning.
It's not yet known why the tram did not slow down enough before the curve on the track.
The RAIB report said the initial investigation "has not indicated any malfunction of the tram's braking system" and that no defects or obstructions had been found on the track.
Victims' families pay tribute
Relatives of five of those killed paid tribute to their loved ones via the British Transport Police Facebook page
. They were named as Donald Collett, Mark Smith, 35, Philip Logan, 52, Robert Huxley, 63, and Dorota Rynkiewicz, 35.
Smith's fiancee Indre Novikovaite, with whom he had a young son, described him as "the best thing that happened in our lives."
The family of Huxley said he was "a larger than life character" and that they were "all heartbroken" by his loss.
London's small tram network, which operates in the south of the city around the Croydon and Wimbledon districts, carries more than 27 million passengers each year along 17 miles of track. Services have been restricted since the crash, which caused some damage to the track and equipment.