AN explosion rocked a McDonald's in France after a large device was discovered in the toilet.

Police have closed roads surrounding the fast food restaurant as they investigate the cause of the alleged blast.

Armed police stand outside McDonald's in the south of France following reports of an explosion Credit: ledauphine.com

Customers were quickly evacuated as emergency services rushed to the scene Credit: ledauphine.com

French media reports there was an explosion at the McDonald's l'Aigle à Grenoble at around midday when "huge flames" were seen coming out of the toilet.

Customers were quickly evacuated while McDonald's bosses took action to inspect its other restaurants.

Flames were seen coming out of the fast food restaurant's toilet after 'explosion' heard Credit: ledauphine.com

So far police have been unable to officially confirm reports of an explosion, but there have been suggestions that a large fire cracker may have caused the blaze.

It is believed diners escaped uninjured, while the toilets were completely destroyed.

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Reports locally suggest around 30 people were in the restaurant and all have since been evacuated.

Other McDonald's restaurants in the city are also apparently set to be inspected.

Officers from Lyon were flown in by helicopter to help determine the cause of the explosion.

One of the main roads through the city remains closed off and the tram line is no longer running between the Louise Michel and Condorcet stations with authorities advising people to avoid the area.

The act has been described as criminal in origin by the local prefecture.

2 A team of officers from Lyon flew in by helicopter to assist with the situation Credit: ledauphine.com

2 The area around the restaurant was left deserted after officials closed it off Credit: Twitter/Toluis7

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