Fire crews remain at the scene of a blaze at Bromley Waste Treatment Centre.
At least 16 firefighters worked through the night, although it was brought under control at about 6pm.
The fire was contained within two large tanks, about eight metres high.
A St John Ambulance spokeswoman told Chris Lynch one person was treated at the scene for minor injuries but was not taken to hospital.
Fire and Emergency Incident Commander, Dave Berry said the fire was not thought to be suspicious, but fire investigations would be back at the scene this morning.
He said smoke reduced overnight, but residents are still being encouraged to keep their windows closed.
Berry said the roof of one tank was made of fibreglass, which collapsed during the fire.
He said there were workmen at the site at the time of the fire.
The treatment plant is still operational.
Staff at the Bromley Waste Treatment Centre have returned to the complex this morning.
Pages Road between Breezes Road and Kerrs Road has reopened.