FIRE investigators are today looking through CCTV to discover what started the blaze at the Grundon waste depot in Ewelme.
About 75 firefighters - including crews from Banbury, Berkshire and Banbury - tackled the blaze at the depot in Goulds Grove for almost six hours last night.
Incident commander Nigel Wilson said it was not yet caused the fire, nor exactly where it started.
However, it is understood the fire started outside and then spread to a sorting building.
It was in an area where hazardous chemicals are stored and a plume of smoke rose high over the site, sparking a warning to people living up to 10 miles away to close their doors and windows.
Mr Wilson said: "It was a fairly substantial fire.
"I would not like to speculate on the cause. Investigators have got CCTV of the entire site and at some point today will establish where the fire started and what caused it."
Firefighters were alerted at about 7.20pm and Mr Wilson said: "The fire was brought under control at about 1am and we had a position where I was comfortable we had put it out by about 3am."
Mr Wilson expected firefighters would leave the depot at some point today.
Reader video from Lu Anthony
A 200-metre safety cordon was put around the depot during the fire.
Reader video from Mark Goldie
- Photos from reader Lu Anthony
Our top stories:
9:52am Tuesday 28th July 2015
A MAN in his 70s was killed in a four-vehicle collision on the A420 this morning, police said.
10:00pm Tuesday 28th July 2015
FOUR people were killed in traffic accidents in 24 hours on Oxfordshire’s roads.
9:59pm Monday 27th July 2015
TWO people died in a car crash on the M40 last night, police have announced.
8:30am Tuesday 28th July 2015
PEOPLE’S bins across Oxford could be rummaged through by council officers on the hunt for evidence to fine people for not recycling properly.
5:10pm Tuesday 28th July 2015
AN AMERICAN dentist has been accused of killing a famous African lion that was part of an Oxford University monitoring project.
1:35pm Tuesday 28th July 2015
A WOMAN was killed in a car accident in Sutton Courtenay yesterday, police have said.