Crews have been on site at Greenway Polymers for more than a week, having been called out just after midday on Monday, April 26, after waste material at the premises near the M54 went up in flames.
Residents and businesses in the area have been advised to keep doors and windows closed, while six schools were told to close last week due to the incident.
Shropshire Fire & Rescue Service has been at the site day and night in efforts to extinguish the blaze, which it said could last up to 10 days.
Crews from Market Drayton worked overnight
At about 1.20am today, a spokesman said: "In attendance at ongoing incident Greenway Polymers near Wellington. Firefighting still underway.
"Crews using main jets to reduce smoke levels in the area – challenging conditions for firefighter."
In attendance at ongoing incident #GreenwayPolymers near #Wellington 🚒 Firefighting still underway 🔥 Crews using main jets to reduce smoke levels in the area 💦 #ChallengingConditions for firefighters 👩🏻🚒👨🏻🚒 Working with colleagues from @SFRS_TelfordCtl #PullingTheNightShift 🌕 pic.twitter.com/3fX4B6yQC1— Market Drayton (@SFRS_MDrayton) May 4, 2021
The fire service predicted the clean-up operation will take months.