Armed police were called to tackle an incident at Three Bridges station.
Alarmed commuters spotted several police cars and two police vans outside the station earlier today.
Sussex Police said officers had been called after concerns were raised about a large group gathering at the station. Officers stopped and spoke to five people and no arrests were made.
A police spokesman said: “Following concerns over a large group of individuals reported to have gathered at Three Bridges railway station officers attempted to engage with them, but many boarded a train to London before they could be spoken with.
“Armed police were among officers to attend, since they do not deal exclusively with firearms incidents but often support colleagues carrying out routine duties.
“Due to the high volume of events taking place this week, there is currently a significant policing presence across Surrey and Sussex and we have been planning well in advance to manage the risk of any disorder.
“Criminal activity will not be tolerated and swift action will be taken against anyone who commits an offence.”