A truck driver miraculously escaped injury when the semi-trailer he was driving became fully engulfed by flames, causing serious traffic delays on the Hume Highway.

Cars banked up on the busy stretch from Sydney to Melbourne as six fire crews worked to extinguish the mail truck near Wagga after it caught alight about 2pm Saturday.

A Rural Fire Service spokesman said trucks from Wagga, Tarcutta and Borambola extinguished the fire within two hours.

HAZMAT teams were called in to clear the fuel off the road and the road was opened later that night.

While the cause of the fire remains unknown, duty officer Inspector Mark Murphy confirmed it wasn’t being treated as suspicious.

Miraculously, the driver sustained no injuries.