Police found a man collapsed outside Hounslow West Underground Station in Cavendish Parade at around 3.36am on Saturday, March 12.
Despite the best efforts of the emergency services, he was pronounced dead at the scene at 4.27am.
He has since been identified as 36-year-old Eovinas Lukosevitius, a Polish national who lived in Hounslow. His next of kin in Poland have been informed.
Initial enquiries suggest Eovinas was involved in an altercation with another man approximately an hour before his death.
A post-mortem examination held on Sunday, March 13 was inconclusive and further enquiries are taking place to establish his cause of death.
Detective Jim Shirley, from the Met’s Specialist Crime Command, said: "Despite an arrest being made we still need to hear from any members of the public who have information about what happened to Eovinas.
"We believe he was in the Hounslow area in the hours leading up to his death and I would ask anyone who saw any suspicious activity to come forward to police."
A 25-year-old man was arrested on suspicion of murder on Monday, March 14. He has since been bailed until a date in April.
Anyone with information is asked to call police via 101 quoting reference CAD 1027/12Mar.