Nearly 100 firefighters are tackling a blaze at an industrial estate.
Crews were called to Long Drive, Northolt, north-west London at around 11.30pm on Monday and multiple units are alight.
London Fire Brigade said 15 engines were sent to the area.
Station manager Ben King said: "This is a very visible fire.
"We would advise nearby residents to keep their windows closed as there is a lot of thick smoke in the area.
"We have a lot of fire engines on the scene so people should avoid the area where possible."
The cause of the fire is currently not known.