Roads around the City of London have been closed by police amid reports of a 'loud bang' near the Heron Tower.
Armed officers and black police vans from the City of London police rushed to the Bishopsgate area following the reports.
Police later confirmed that the incident was likely caused by an explosion of a boiler.
One bystander said debris fell from the 46-storey skyscraper onto the street following a large bang on the roof.
Richard Metcalfe said on Twitter: "Was in an external facing room in the Heron Tower - heard the bang then saw something fall and what looked like torn up paper float pass. Sounds like it's just something from the roof."
Another said: “Not sure what’s going on at Heron Tower, but we heard the massive bang in our office just up the road. It spooked us all.”
Traffic was closed in both directions on the busy arterial road as cops put up cordons to deal with the incident, which was later lifted.
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Videos from the tower show a large police presence and the diversion of cars and buses from the area.
The City of London Police said: "Camomile St, Bevis Marks and Dukes Place are currently closed in both directions due to @CityPoliceCops responding to an ongoing incident.
"Thank you for your patience; updates to follow."
The Heron Tower, recently renamed the Salesforce Tower, is home to a number of popular restaurants and clubs.
The building became an iconic feature of the city's skyline following its completion in 2008.
