A two-truck smash has caused hundreds of litres of diesel to spill onto the Hume Highway near Bowning, firefighters say.

One person sustained minor injuries when the two northbound b-double trucks crashed about 6.30am on Wednesday morning, NSW Police said.

Firefighters are working to contain up to 400 litres of spilt fuel, just south of the Lachlan Valley Way turnoff.

Drivers are advised to reduce speed and exercise caution although traffic is flowing freely.

In a separate incident, a large amount of fuel spilled onto the highway near Goulburn after two trucks collided about 2.30pm.

Northbound traffic was delayed after the vehicles crashed and one truck caught fire near Tiyces Lane at Boxers Creek.

No-one was injured. Police had left the scene by about 3.30pm.