London Fire Brigade said on Tuesday that 15 fire engines and around 100 firefighters have been called to tackle a fire at a factory on Rigby Lane in Hayes.
There are no reports of injuries, Station Commander Dean Wilkinson said, adding that the firefighters are working swiftly to bring the fire under control.
The cause of the fire is not known at this time, London Fire Brigade said on its website.
A factory containing around 400 tonnes of waste recycling is alight, it said, adding around 10 gas cylinders had been removed as a precaution as some could explode when exposed to heat.
Details on the extent of damage were not known. London Fire Brigade did not respond to a Reuters request for comment outside office hours.
(Reporting by Anirudh Saligrama in Bengaluru; Editing by Himani Sarkar and Tom Hogue)
