A truck crash in Poland has left a highway covered in 12 tonnes of liquid chocolate, blocking traffic in both directions and creating headaches for clean-up crews.

The tanker overturned in the early hours of the morning after colliding with a traffic barrier in Graboszewo in the country's west on Wednesday (local time), causing waves of the sugary liquid to coat Poland's A2 motorway between Wrzesnia and Slupca.

Traffic came to a complete standstill in both directions, with police saying it could take several hours to reopen the road.

Rescue officials said the liquid chocolate was solidifying as it cooled and would require large amounts of hot water to clear away.

"The cooling chocolate is worse than snow," said Slupca fire brigade senior brigadier Bogdan Kowalski.

According to the manufacturer, spilled chocolate is more difficult to remove than oil and needs to be shifted gradually using pressurised hot water.

In some areas, the chocolate was so thick that heavy machinery was brought in to scoop up the mess.

The driver suffered a broken arm and was taken to hospital.

While no-one else was injured during the incident, the troublesome substance did rob one local journalist of his shoe.

ABC/wires