Charing Cross station in London has been closed and around 1,450 people evacuated from a nightclub and a hotel because of a gas leak.
Witnesses said there was "chaos" as doormen at the Heaven nightclub ordered guests to leave.
Other clubs, hotels and businesses in the area of the West End around The Strand have also been evacuated with disruption for rush hour commuters expected.
Emergency services were on the scene shortly after 2am after high levels of natural gas were detected in Craven Street near Charing Cross station.
Network Rail says the station will remain shut until further notice.
A London Fire Brigade spokesman said: "We are assisting police on the Strand after a ruptured gas main was discovered using detection equipment and high levels of natural gas were detected in the atmosphere.
"As a precaution, approximately 1,450 people have been evacuated. They are from a hotel and a night club.
"The Strand is completely closed and we are asking people to avoid the area.
"We do not know the cause of the gas leak at this stage. It is ongoing and engineers are down at the scene trying to isolate the leak. There are still high readings of natural gas in the area.
"We are working to sort it out as quickly as possible."
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The Metropolitan Police tweeted: "A cordon and road closures are in place as a precaution and members of the
public/motorists are advised to avoid the area at this time."