Twitter user Helen True shared this photograph of emergency services attending London Bridge station where four people were taken ill.
Network Rail and TfL dismissed reports of a gas leak and said that overground and underground train services were running as normal.
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Paramedics attended a scene in Willesden, north-west London, on Monday afternoon where they found the teenager with stab wounds.
The popular game relies on Google Maps, a problem in South Korea as those functions are limited by the government.
A Met Office warning covering much of England and south-east Wales is expected to remain in place until 11am.