SA's Bangor fire continues to burn

South Australian crews have been back-burning overnight to try to stop the Bangor bushfire in the Southern Flinders Ranges from reaching towns.

The CFS on Monday issued an emergency warning for residents in Laura, Stone Hut and Wirrabara, but downgraded it to a watch-and-act alert on Monday night.

The Bangor blaze, which started more than three weeks ago, has burnt more than 33,000 hectares of scrub.

The CFS on Tuesday morning said the fire is travelling in an easterly direction towards Laura, Stone Hut and Wirrabara.

Back-burning on the eastern side of the fire took place overnight and people in the Laura area may see an increased amount of smoke.

CFS co-ordinator Brenton Eden told ABC Radio the back-burn had established a very effective control line around the spot fires.