Spray cans have been found near where three people died after being struck by a train.
The incident occurred on tracks near Loughborough Junction station, south London, which is an area popular with graffiti artists.
British Transport Police (BTP) were called to the scene at 7.30am on Monday but rail industry sources told the Press Association the paint was found nearby and the three people may have been killed overnight, when freight trains operate.
Officers were seen taking photographs of graffiti as part of their inquiries.
The bodies were found on an elevated section of track with an electric third rail between Brixton and Denmark Hill.
BTP stated that they were hit by a train but was unable to confirm whether it was a freight or passenger service. There were no reports of any passenger trains being involved.
Det Supt Gary Richardson said: “My team are now working hard to understand what happened and how these three people came to lose their life on the railway.
“My thoughts are with the family and friends of these three people.
“At this time, we are treating their deaths as unexplained as we make a number of immediate inquiries.
“I would ask anyone who was near to Loughborough Junction this morning, and saw something which they think might be relevant, please contact us as soon as possible.”
Preliminary investigation
Rail regulator the Office of Rail and Road has opened a preliminary investigation.
In a press conference held near the scene, Supt Matthew Allingham of BPT said: “We were called at 7.34am this morning to Loughborough Junction to reports that three bodies had been found on the track. Officers attended and sadly three men were declared dead at the scene.
“It is believed they died earlier in the morning and injuries are consistent with being hit by a train. Officers have delivered the sad news to one family as we believe one of the men was their son.
“However we are still working to identify and locate the next of kin for the other two men. All three men are believed to be in their 20s.
“Our investigation is focusing on how and why the men came to be on the tracks in the early hours of this morning.
“It is far too early for us to comment on the reasons for them being there.”
The first call to police was made by a train driver, Mr Allingham told reporters.
He went on: “We know they were dead for a while before we turned up, it is a possibility that it was during the hours of darkness that’s why it wasn’t reported earlier.
“We’re still trying to identify the train that actually hit the individuals.”
Regarding the spot where the trio were found, Mr Allingham added: “There isn’t a sort of safe refuge up there, so if somebody was on those tracks there wouldn’t be anywhere for them to go to avoid the train.
“As far as I understand it, if they’ve been caught in that section of track when a train came through then they really wouldn’t have had much options.”–PA