A bush fire over 1km long is raging in the Canterbury Plains this evening.

Firefighters were sent to the blaze off Rakaia Terrace Rd about 3.30pm with nine appliances dispatched.

Fire Service southern communications centre shift manager Tim Reynolds said firefighters were sent to a blaze in same area earlier in the week but it was not clear whether this was the same fire.

It was not thought to be threatening any properties at this point.