Up to 100 firefighters have been tackling a blaze at a railway arch in Bromley-by-Bow.
Eleanor Street was cordoned off while 10 emergency crews from fire stations across east London dealt with the incident off Bow Road.
The fire broke out in the arch at 10.35am on April 1, sweeping through a manufacturing workshop on the mezzanine floor.
Damage is said to have been light, but precautions are being taken as the fire is under tracks on the Fenchurch Street to Stratford rail link where it crosses over the London Underground between Bow Road and Bromley-by-Bow stations.
District Line services are unaffected.
Emergency crews were brought in from Shadwell, Bethnal Green, Whitechapel, Poplar and other east London fire stations.
Investigators are looking into the cause of the fire.
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