British Transport Police said that the woman killed after being hit by a train in south London was believed to be in her thirties.
Her son, who also died following the collision, is thought to have been three years old.
Senior Investigating Officer Detective Chief Inspector Iain Miller said:
Our thoughts remain with the family and friends of the woman and child involved in this tragic incident.
Officers are continuing to work to establish the full circumstances surrounding the incident, although early indications show that no one else was believed to have been involved.