A driver has been left devastated after his semi-trailer carrying a load of cattle caught alight on the NSW North Coast, ending in tragedy for some of the animals.

The semi-trailer caught fire on the Bruxner Highway at Wollongbar, in the state’s Northern Rivers region, just before midday on Thursday.

Inside the trailer were more than 60 cows.

Witness Adam Wijeyekoon told 7NEWS.com.au that the truck driver put himself in “serious danger” to climb inside the trailer to unload the top deck to save the cattle.

“Unfortunately, due to the commotion, tyres exploding, thick black smoke, a few wouldn’t move,” Wijeyekoon said.

“The driver was clearly distraught by the loss of cattle, and his truck is likely totalled.”

Meanwhile, a video showed thick, black smoke and bright orange flames pouring from the side of the truck as bystanders who blocked the road screamed for the cattle to be freed.

“Open the gate … let them out, let them out,” drivers yelled.

“We’ve got the traffic stopped just let them out.”

“Three FRNSW fire trucks and around 12 firefighters from Lismore and Goonellabah Fire Stations responded, supported by a FRNSW Inspector. NSW Police, NSW Ambulance and the Rural Fire Service (RFS) also attended,” Fire and Rescue NSW said in a statement.

“Firefighters deployed multiple hose lines to contain and extinguish the blaze, while also managing a diesel leak from the vehicle.”

The blaze was brought under control just after midday.

NSW Fire and Rescue said the cattle that escaped were herded before the fire enveloped the entire truck.

The animals were secured in a nearby paddock.

A vet was requested to attend to the animals, Fire and Rescue NSW said.

“Once Firefighting operations concluded, crews then worked to safely decant approximately 400L diesel from the truck’s fuel tanks,” Fire and Rescue NSW said.

The highway has since reopened but Live Traffic NSW said: “All westbound lanes are open. One of two eastbound lanes remains closed for vehicle recovery. Allow some extra travel time.”