Heavy smoke and fog caused a two-car crash on the Kings Highway between Queanbeyan and  Bungendore.

The crash occurred at about 7am, Wednesday morning on the Burbong Bridge crossing the Molonglo river.

Monaro police and ACT police closed the highway until further notice. It was reopened about 9am.

The smoke was coming from a nearby prescribed burnoff in the Kowen Forest.

There were no injuries reported.

Police urge motorists to drive with extreme caution and to heed advisory signs and road closures.