Loire-Atlantique, the department which is home to France's eighth biggest city of Nantes, is part of the Pays-de-la-Loire region.
But it appears many people living there want to be part of the neighbouring region of Brittany instead.
This week, the department's local authorities said that they were looking into the issue after the organisation Bretagne Réunie (reunited Brittany) handed a petition on the matter to the government last month. It was signed by 100,000 people and because that number makes up one tenth of the department's electorate, local authorities have to look into it by law.
“We cannot ignore such an important demand and I have taken into account the citizens' requests through this petition,” the department's president Philippe Grosvalet told Le Monde.
The desire of people in the Loire-Atlantique to become Breton isn't new.
The department was part of Brittany until the Second World War, when it was separated and made part of the neighbouring region by the Vichy government. That region eventually became the Pays-de-la-Loire in 1955.
The issue has always been simmering since then and pro-Breton voices have become louder in recent years as they hope to take advantage of a law that allows departments to chose which region they belong to via a referendum.
Over the last 18 months, Bretagne Réunie and other organisations have been trying to rally citizens to their cause. In September, over one thousand people marched in Nantes to ask for a referendum.
“It's so obvious to us that we're Breton that it really hurts when people tell us that 'no, we're not,” Romain Bily of Bretagne Réunie told French media.
However, there's very little chance however of the change actually happening, experts say.
The referendum would have to be approved by a number of different government administrations, including the Pays de la Loire region. And given that the Loire-Atlantique is the region's most populated and wealthiest area, it's unlikely it would agree to losing it.