Fire crews are asking Marlborough locals to stay away from the scene of a major blaze.

The fire has been burning since Wednesday, across around 450 hectares in the Waikakaho Valley, north of the Wairau River.

Crews have been working through the night, and have about half the perimeter under control.

But incident controller Rob Hands said they need the public to stay away and let firefighters do their job.

"We've had really good support from the public, but we still don't want people on the fire site and there's a total fire ban on. So don't use any fire out there, we've got enough to do."

He reported overnight crew worked to keep the fire contained.

"The night crew are predominantly there to patrol the perimeter and ensure the properties are safe from any flare ups."

About 50 firefighters are fighting the fire this morning.