A visually impaired man died when he was hit by a train after falling from a station platform, investigators said.
The unnamed victim died at Eden Park station, near Bromley, south-east London on 26 February.
The platform did not have a tactile surface designed to warn people with poor vision they were close to the edge, the Rail Accident Investigation Branch (RAIB) said.
Southeastern said it was co-operating with the RAIB investigation.
Eden Park is operated by the train company and the train that struck the man was also part of the Southeastern fleet.
Investigators said he fell from the platform and was "struck almost immediately" by the train running from Hayes to London Charing Cross.
The RAIB inquiry will aim to identify the sequence of events and consider factors relating to the provision of tactile surfaces on station platforms.
A spokesman for Southeastern and Network Rail said: "We are fully co-operating with the RAIB investigation regarding the death of a man at Eden Park station on 26 February.
"We appreciate the efforts of all the emergency services and our staff who attended this tragic incident. Our thoughts remain with his loved ones."