The woman and girl killed by a high speed train at Ealing Broadway were mother and daughter, police have confirmed.
Horrified commuters described "sickening screams" after the 36-year-old woman and her 16-year-old daughter were hit by the train travelling from Cardiff to Paddington on Tuesday evening.
Commuters at the scene described it as a "nightmare" as emergency services flooded the area at the height of rush hour.
Police have said they are not treating the deaths as suspicious.
Superintendent Chris Horton, of British Transport Police, said: "Shortly before 6.10pm on Tuesday, 23 June, we were called to Ealing Broadway station following reports of a person struck by a train.
"Officers attended, alongside colleagues from the Metropolitan Police Service and London Ambulance Service (LAS) and discovered two people had been struck and killed by a train.
"Since the incident, officers have been working to determine the identities of the deceased and the details of the moments leading up to their deaths.
"As a result of those enquiries we are now able to confirm that the deceased have been identified as a 36-year-old woman and a 16-year-old girl, who were mother and daughter. We can also confirm that we are not treating the deaths as suspicious and we will assist in the compilation of a report for the coroner.
"Our thoughts are now with the family and we have specialist officers with them providing support and guidance at what is clearly a difficult and traumatic time.
"The family are struggling to come to terms with what has happened and ask that they be allowed to grieve privately and, in line with those wishes, we are not in a position to release any names at this stage."
London Fire Brigade (LFB) said it was called to reports that an adult and child had fallen on to the tracks at Ealing Broadway , shortly after 6pm.
Eyewitnesses described seeing at least one woman stood on the edge of the platform moments before the collision.
Taz Phalora, 22, from Ealing , was on his way home when he witnessed the tragedy.
He told Mirror Online : "I was waiting for my train and there was probably about 50 or 60 people on the platform.
"Out of the corner of my eye, I saw someone pretty close to the track for the high-speed line behind me.
"Seconds after I turned back around I heard a massive thump and then people started screaming.
"I left just as the fire engines were turning up but I just wanted to get home, it was a horrible experience."
Another eyewitness, who asked not to be named, said: "I didn't see them fall but I heard a loud bang and the train sounding its horn.
"The screams were sickening and people were all looking over the edge of the platform."
Police have appealed for witnesses or anyone with information to come forward.
LAS said staff including its hazardous area response team had been sent to the station but that two people had been pronounced dead at the scene.
Following the incident, Heathrow Express said all services between Paddington station and Heathrow airport had been suspended, while First Great Western said there were delays of up to 90 minutes to and from Paddington.
