Police have closed a section of Main South Road, Hornby, due to a fire at Ravensdown fertiliser plant.

Newstalk ZB reporter Rachel Das is on Main South Road.

"It looks like a massive factory roof, I can't see many flames but I can see thick black smoke filling the sky."

Talkback caller Stu told Chris Lynch it looked like smoke could be heading towards Christchurch Airport

"It would have be to 100m in the air and drifting towards the airport."

The public are urged to avoid the area.

More details to come