Mystery remains over the cause of a large haystack fire which crews have worked through the night to extinguish.

Firefighters were first called to the scene in Hulberry, Eynsford near the M25, just after 5pm on Monday.

At its height, the blaze could be seen from the motorway and four fire engines, along with a bulk water carrier were sent to the scene to prevent it spearing to nearby property.

Crews estimated about 300 tons of hay was alight.

Attendance was soon reduced to two fire engines, while the fire was allowed to burn out under controlled conditions.

One fire engine remained on the scene overnight to monitor the fire and was still there this morning.

A spokesperson added: "There were no casualties and the cause is not yet known."