People living in and around Oxford have been left startled after seeing what has been described as "an explosion".
Householders and motorists have shared videos of the sky being lit up on Monday evening from around 7pm.
One eyewitness said: "Saw this strange pulsing sky out of our windows looking north west of Oxford. I’m guessing it’s a fire caused by the lightning storm that passed over."
A statement from Severn Trent Green Power released just after 8.30pm on Monday confirmed a digester truck had been struck by lightning around 7.20pm.
This took place at the Cassington AD Facility near Yarnton.
The statement said: "We can confirm that at around 7.20pm this evening, a digester tank at its Cassington AD facility near Yarnton, Oxfordshire, was struck by lightning resulting in the biogas within that tank igniting.
"We are working with the emergency services to secure the site and will provide further comments in due course."
Thames Valley Police has confirmed officers are at the scene.
A statement said: "Our officers are currently at the scene of a fire at a waste plant near Yarnton, Oxfordshire.
"It is believed that lightning struck gas containers at the site during bad weather this evening, causing a large fire."
Oxfordshire Fire and Rescue Service was also called to the incident at 7.17pm.
Six fire engines, 40 fire and rescue personnel attended as well as an aerial appliance and water tanker.
Fire and rescue operations are ongoing and a spokesman for the service said there would be no further updates this evening.
It comes as rain has been falling throughout the evening accompanied by lightning strikes.
Another eyewitness said: "I don't know what it was but it was massive. There were lots of fire brigade and police cars minutes later going along the A40."
The Met Office had issued a yellow weather warning for thunderstorms in Oxford this evening.
One householder Katty, whose surname has not been disclosed, said: "The lights all flickered in the house and the sky lit up."
Oxfordshire Fire and Rescue Service and Thames Valley Police have been contacted for comment.