A fire broke out late on Wednesday morning at a recycling plant in Haren, emergency services have confirmed.
The blaze started in a 2,500-square-metre warehouse on Chaussée de Buda.
The site houses a company that recycles electrical and electronic equipment.
The fire has caused traffic congestion on nearby roads, particularly on Chaussée de Vilvorde, according to Brussels-Capital/Ixelles police.
A security perimeter has been set up around the site.
Residents in the area have been asked to keep their doors and windows closed.
