British Transport Police has issued images of three people they want to speak to following the attack at Elm Park tube station on February 24.
The victims were left needing hospital treatment following the incident at just after 8pm.
Their injuries are not thought to be life-threatening or life-changing.
Images from CCTV show two men and a woman.
One of the men is wearing a black puffer jacket along with a black face covering and black baseball cap.
The other male can be seen wearing a black coat.
The woman is wearing a cream jacket, blue jeans and converse trainers, while also holding a green coat.
Investigating officer Detective Inspector Marvin Bruno said: “Violence in any form will not be tolerated on the rail network and we would like to reassure the travelling public that our officers are working tirelessly to identify and apprehend those responsible.
“We are really keen to speak to the people in the images, or anyone else who witnessed the incident, as we believe they have information which could help our investigation.
“If you know them or have any information that might help, please get in touch.”
Anyone who recognises them, or has any other information, is asked to contact British Transport Police by texting 61016 or by calling 0800 40 50 40 quoting reference 803 of 24/02/24.
Alternatively, you can call Crimestoppers anonymously on 0800 555 111.
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