Two suspected vandals have been killed by a London Underground (LU) train in Barking, east London.
The train was entering the sidings for the night
British Transport Police (BTP) said the pair, aged 19 and 21, were hit by a District Line train at Barking depot at 2306 GMT on Friday.
Police said a group of men were seen spraying graffiti nearby moments before the crash, but stressed they were not being chased by security guards.
A 23-year-old man was arrested near the scene on suspicion of criminal damage.
A spokesman for London Ambulance Service said the pair were pronounced dead at the scene.
Ch Supt Paul Crowther said that although a security guard spotted a group spraying graffiti, which may have spurred them to flee, they were "not being chased".
He said: "It appears that they ran into the path of the train having emerged from a nearby depot. The train driver did try to stop but was unable to do so."
Describing the incident as "tragic" he said it showed that spraying graffiti was a "dangerous pastime".
A man who lives in a block of flats opposite the tracks where the incident happened said he saw the bodies from his kitchen window.
John Leitch said: "I came out to my kitchen window and saw that there was a train there where normally there isn't one.
"The train moved off and I could see that there were two bodies on the track. They looked like young men."
He added that emergency services had to wait until the power on the lines was turned off to reach the bodies.
They were moved from the tracks early on Saturday morning.
A two-metre fence with barbed wire on it surrounds the Barking station, but Ch Supt Paul Crowther said he was not sure how the group entered the depot despite this.
He added that increased security across stations in London ensured fewer incidents of vandalism.
London Underground said services between East Ham and Dagenham on the District Line were suspended on Friday night following the incident but they were resumed at 0800 GMT on Saturday.