Residents have been warned to stay indoors after it emerged a breakers' yard that went up in flames may have contained asbestos.
About 60 firefighters from Oxfordshire Fire & Rescue tackled the blaze at T&B Motors in Witney, on Wednesday.
West Oxfordshire District Council has warned people to "avoid unnecessary outdoor activity" during the clean-up operation.
However, a spokesman said there was "no significant public health risk".
Plumes of black smoke were visible over the town for hours during the blaze.
Thames Valley Police said the cause of the fire was not thought to be suspicious.
The force thanked fire crews and the "fabulous" residents of the town for their help during the blaze.
The West End area of the town remains closed to through traffic, but people have been allowed to return to their homes.
We would like to give a big shout out to the fire crews who worked so very hard yesterday 👏 pic.twitter.com/APCBk4GAPv— TVP_WestOxon (@TVP_WestOxon) June 14, 2018
We must say a big thank you to the residents of witney for all the tea, coffee and food you provided us with, it was very much appreciated by all the 999 staff. You really are a fabulous bunch. #community #thankyou— TVP_WestOxon (@TVP_WestOxon) June 14, 2018
The extent of the contamination is currently being investigated, with part of Farmers Close cordoned off.
A council spokesman said: "Nearby residents are being advised that the building potentially contained some asbestos cement roof tiles and an appropriate cleanup of the site and vicinity is taking place."
As long as "appropriate cleanup procedures" were followed there was "no significant public health risk" but airborne asbestos fibres "may pose a risk to those inhaling them", the spokesman added.
The council's advice to residents includes:
- Not letting children play outside, and avoiding unnecessary outdoor activity
- Closing all external doors and windows
- Refraining from putting washing out or going in gardens
- Not touching any of the debris from the fire