Pokemon Go: Network Rail has 'safety concerns' for gamers
Nintendo and app developers have been contacted by Network Rail over "safety concerns" regarding Pokemon Go being playable close to live train tracks.
The BBC understands gamers have been walking on to the tracks at Birmingham New Street.
Network Rail has warned that trains can reach high speeds and gamers "are likely to be distracted" when playing.
Pokemon Go developers, US firm Niantic, has not yet responded to questions from the BBC.
Network Rail, which has put up warnings on electronic signs at New Street, controls 2,500 stations as well as tracks, tunnels and level crossings and says trains can reach speeds of 100mph (160kmh).
British Transport Police (BTP) said it had no records of trespass at Birmingham's central station related to Pokemon Go but warned of the dangers it can pose.
The online game - which is attracting millions of players - involves finding virtual Pokemon characters in real locations across the world.
Some of those locations have been designated as PokeStops, which players visit to collect items during the game, and PokeGyms, where gamers go to train their virtual monsters.
Lisbeth Fromling, chief health and safety officer at Network Rail, said: "We do have safety concerns around the locations of certain PokeGyms and PokeStops which we believe are too close to the working railway.
"We are concerned that by playing the game on or very close to our infrastructure, young people are likely to be distracted and even less aware than usual of the risks around them.
"We are in the process of making contact with the app developers and with Nintendo to share our concerns in the hope that we can work together to make the app safer."