A truck driver is missing after two heavy vehicles collided and caught fire on the Hume Highway near Gunning early on Friday.

Police say a road train and a B-double collided in the northbound lanes at Breadalbane about 4.10am.

The 31-year-old driver of the road train was treated for minor injuries and taken to Yass Hospital for mandatory testing.

The driver of the B-double remains unaccounted for.

The Hume Highway has been closed in both directions, with traffic diverted via the Federal and Barton highways through Canberra.

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