A major fire under a bridge near the US city of Atlanta has caused a large section of motorway to collapse.

The city's fire and rescue agency confirmed a portion of the Interstate 85 highway had collapsed.

There were no immediate reports of casualties but Atlanta Fire and Rescue said all lanes were blocked and told residents to avoid the area.

The governor's office also said no one had been injured.

Local TV images showed thick black smoke billowing into the sky.

It was not immediately clear what was burning but images appeared to show barrels and coils under the bridge.

Fire-fighting vehicles were said to be using foam from Atlanta's Hartsfield-Jackson International Airport usually used to put out fires in plane crashes.