An armed gang held up a van transporting 70 kilograms (154 pounds) of powdered gold in a dramatic heist near the French city of Lyon on Monday.

Armed with assault rifles, the assailants then grabbed the sacks of gold, loaded it into a getaway car, set fire to the other vehicle and sped off.

The police initially said the robbers trapped the two guards transporting the gold in the back of their van but later revised that account, saying they were not locked up.

The fire gutted the abandoned car and three nearby vehicles but the guards escaped unharmed.

Transport company Loomis said the van was carrying "industrial raw materials".

The value of the loot was estimated at 2.5 million euros ($2.6 million).

The robbery took place at an exit from the A6 motorway that connects the city with Paris.

France has experienced a growing number of motorway hijackings in recent years.

In March 2015, a group of around 15 robbers held up two vans carrying jewellery worth around nine million euros ($9.5 million) at a toll booth on the A6, near the central city of Auxerre.

More recently, two Qatari women were held in their chauffeur-driven Bentley after leaving Le Bourget airport north of Paris in November. The masked robbers made off with valuables worth more than five million euros in jewels and other valuables.