A huge fireball rips through the Oxford sky Twitter / @stuartbigbro2
A social media user claimed: "There were lots of fire brigade /police cars minutes later going through A40."
However, Oxfordshire was named as one of the counties at risk from a yellow weather warning for thunderstorms.
The Met Office said: "Thunderstorms with frequent lightning have already affected parts of the warning area, these continuing into the evening in places.
"An increasing risk of longer-lasting intense downpours too, especially later this evening and further east across the warning area, for example towards south Lincolnshire and East Anglia.
"These storms are likely to be focused in relatively narrow bands, so some places will miss the worst, while a few locations might catch 25-50 mm of rain within 2 or 3 hours, along with frequent lightning and gusty winds."
The Met Office's yellow thunderstorm warning
Thames Valley Police confirmed the current theory is lightning struck gas containers at a waste plant near Yarnton.
Severn Trent Green Power said a digester tank at its Cassington AD facility was struck by lightning resulting in the biogas within that tank igniting at around 7.20pm.
Severn Trent Green Power added: "Thankfully no one has been hurt and we are working with the emergency services to make sure the site is safe so that we can assess the damage as soon as possible."
Residents near the Yarnton facility have reportedly been urged to keep their windows closed while emergency services continue to tackle the ongoing blaze.