A fire under a major London rail hub is causing travel chaos this morning. The fire broke out under the tracks near London Bridge station and forced trains traveling in and out of the busy junction to stop. Footage posted on social media showed a large response from emergency services in the Southwark area and a thick plume of smoke rising over the capital. The fire broke out in an arched building on Union Street, just below a major railroad crossing. Lines serving the south of the capital are completely blocked and may be out of action for the next few hours. Services on the Jubilee Line, which runs through Southwark and London Bridge stations, have been partially suspended. Transport for London warned of serious delays and said trains would not serve stations between Green Park and Canary Wharf. Tube stations at Southwark and London Bridge have been evacuated and closed. The fire broke out in the London Bridge area of central London, close to railway lines (Image: @timlevell) The fire broke out on Union Street, just below a major railway crossing (Image: Google) To view this video, please enable JavaScript and consider upgrading to a web browser that supports HTML5 video The fire started in an arch under a long railway line (Image: @NetworkRailSE) A man eating breakfast with his mother nearby said he heard an explosion before the fire started. He told Metro.co.uk: “We heard a fairly loud bang of some sort and then saw smoke rising everywhere along with a noxious, toxic smell. “We evacuated – along with everyone else in the restaurant – and saw part of a building on fire. “I don’t know where the fire came from, but there was definitely a loud sound and debris that made it look like there had been some kind of explosion.” Network Rail confirmed major disruption, adding that “services are being diverted to other London terminals or terminated at alternative locations”. Ewer Street Junction, four lines carrying Thameslink and South Eastern Railway trains in and out of the capital, was completely blocked by the fire and long delays are expected to continue. Smoke can be seen billowing over the tracks, rendering the route unusable (Image: @NetworkRailSE) Several fire crews are at the scene to tackle the blaze (Image: @LondonFire) To view this video, please enable JavaScript and consider upgrading to a web browser that supports HTML5 video A witness at the scene said people in nearby buildings had to be evacuated The London Fire Brigade confirmed ‘the railway arch is completely burnt’ (Image: @LondonFire) A spokesman said the tracks would have to be inspected once the fire was out before services could resume. The departures board of the London Bridge train services was in great disarray. A London Fire Brigade spokesman said: “Six fire engines and around 40 firefighters have been called to a fire on Union Street in [Southward].’ Station Commander Wayne Johnson, who is at the scene, said: “The fire is producing heavy smoke and those who live or work in the area are advised to keep their windows and doors closed. “Trains to and from London Bridge are affected and many buildings have been evacuated.” A spokesman for British Transport Police said: “Southwark station is closed and there is a cordon on America Street and Great Suffolk Street.” Contact our news team by emailing us at [email protected] For more stories like this, check out our news page.