Three people have died after being struck by a train.
British Transport Police (BTP) were called to Loughborough Junction station, near Brixton in south London, at 7.30am on Monday.
They described the deaths as "unexplained".
Officers remain at the scene, where they are working to identify those killed and inform their families.
A "number of inquiries" are being carried out by BTP to establish how they came to be on the tracks.
Detective Superintendent 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."